diff --git a/changelog.d/msp-abd-spouse-income.fixed.md b/changelog.d/msp-abd-spouse-income.fixed.md
new file mode 100644
index 00000000000..f51776f4faa
--- /dev/null
+++ b/changelog.d/msp-abd-spouse-income.fixed.md
@@ -0,0 +1 @@
+Apply SSI's eligible-couple and spouse deeming rules to Medicare Savings Program countable income and the poverty guideline when only one spouse is on Medicare, including a spouse who is aged, blind or disabled.
diff --git a/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_countable_income.yaml b/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_countable_income.yaml
index fb81c53bf64..8b63696d1bd 100644
--- a/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_countable_income.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_countable_income.yaml
@@ -339,8 +339,9 @@
   output:
     # PM 15-04-03-a: one applicant, so one $25. Deemed: unearned 600 - 25 = 575;
     # earned (2,500 - 65) / 2 = 1,217.50; 575 + 1,217.50 = 1,792.50.
-    # The spouse without Medicare: (2,500 - 25 - 65) / 2 = 1,205.
-    msp_countable_income: [1_792.5, 1_205]
+    # The spouse without Medicare has person1's $600 deemed the same way, since
+    # 600 is above the 497 rate difference.
+    msp_countable_income: [1_792.5, 1_792.5]
 
 - name: Case 16, Illinois caps a spouse's 25 dollar exemption at that spouse's income.
   period: 2026-01
@@ -454,5 +455,415 @@
     # SSI methodology deems the spouse's wages whether or not the person
     # meets SSI's noncitizen test: 20,000 > (1,450 - 967) x 12 = 5,796.
     # (1,000 - 20) + (1,666.67 - 65) / 2 = 980 + 800.83 = 1,780.83.
+    # person2 has person1's income deemed the same way: 12,000 > 5,796.
     is_ssi_spousal_deeming_applies: [true, false]
-    msp_countable_income: [1_780.83, 790.83]
+    msp_countable_income: [1_780.83, 1_780.83]
+
+- name: Case 21, income of a disabled spouse who is not on Medicare counts for the couple.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 12_000
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_unearned_income: 18_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+  output:
+    # (1,000 + 1,500) - 20 = 2,480, above 135% of the two-person guideline:
+    # 1.35 x 1,803.33 = 2,434.50.
+    is_medicare_eligible: [true, false]
+    ssi_couple_computation_applies: [true, true]
+    msp_countable_income: [2_480, 2_480]
+    msp_category: [NONE, NONE]
+
+- name: Case 22, Illinois gives one exemption when only one spouse is on Medicare.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 12_000
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_unearned_income: 18_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: IL
+  output:
+    # (1,000 + 1,500) - 25 = 2,475.
+    msp_countable_income: [2_475, 2_475]
+
+- name: Case 23, a disabled spouse living apart in a facility is not counted.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 12_000
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_lives_in_medical_treatment_facility: true
+        ssi_medicaid_pays_majority_of_care: true
+        ssi_unearned_income: 18_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+  output:
+    # 20 CFR 416.414(b)(3) computes the spouses separately: 1,000 - 20 = 980.
+    ssi_couple_computation_applies: [false, false]
+    msp_countable_income: [980, 1_480]
+
+- name: Case 24, allocations for ineligible children come off the spouse's income before deeming.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 12_000
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_unearned_income: 18_000
+      person3:
+        age: 12
+      person4:
+        age: 10
+    tax_units:
+      tax_unit:
+        members: [person1, person2, person3, person4]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+      child1_marital_unit:
+        members: [person3]
+      child2_marital_unit:
+        members: [person4]
+    households:
+      household:
+        members: [person1, person2, person3, person4]
+        state_code: TX
+  output:
+    # 20 CFR 416.1163(b): two allocations of 1,491 - 994 = 497 total 994.
+    # person1: 1,500 - 994 = 506, above 497, so it is deemed (416.1163(d)(2)):
+    # 1,000 + 506 - 20 = 1,486, at or below the two-person 21,640 / 12 = 1,803.33.
+    # person2: 1,000 - 994 = 6, not above 497, so 1,500 - 20 = 1,480 alone.
+    msp_countable_income: [1_486, 1_480, 0, 0]
+    msp_fpg: [1_803.33, 1_330, 1_330, 1_330]
+    msp_category: [QMB, NONE, NONE, NONE]
+
+- name: Case 25, a disabled spouse's income at or below the rate difference is not deemed.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 20_400
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_unearned_income: 5_400
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # 20 CFR 416.1163(d)(1): person2's 450 is not above 497, so person1 is tested
+    # alone: 1,700 - 20 = 1,680 against the one-person 15,960 / 12 = 1,330.
+    # 120% is 1,596 and 135% is 1,795.50, so QI.
+    # person2 has person1's 1,700 deemed: 450 + 1,700 - 20 = 2,130.
+    msp_countable_income: [1_680, 2_130]
+    msp_fpg: [1_330, 1_803.33]
+    msp_category: [QI, NONE]
+
+- name: Case 26, an eligible SSI couple is tested together when one spouse is on Medicare.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 16_800
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # 20 CFR 416.1801(c): 1,400 - 20 = 1,380 is below the 1,491 couple rate, so each
+    # spouse is eligible for SSI: (1,491 - 1,380) / 2 = 55.50.
+    # 1,380 is at or below the two-person 1,803.33, so QMB. Tested on the one-person
+    # 1,330 instead, person1 would be SLMB.
+    uncapped_ssi: [55.50, 55.50]
+    msp_countable_income: [1_380, 1_380]
+    msp_fpg: [1_803.33, 1_803.33]
+    msp_category: [QMB, NONE]
+
+- name: Case 27, income at or below the rate difference is not deemed from a spouse who is not aged, blind or disabled.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 20_160
+      person2:
+        age: 50
+        is_tax_unit_spouse: true
+        ssi_unearned_income: 5_400
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # 20 CFR 416.1163(d)(1): person2's 450 is not above 497, so person1 is tested
+    # alone: 1,680 - 20 = 1,660 against the one-person 1,330.
+    # 120% is 1,596 and 135% is 1,795.50, so QI. The two-person 1,803.33 would be QMB.
+    # person2 has person1's 1,680 deemed: 450 + 1,680 - 20 = 2,110.
+    msp_countable_income: [1_660, 2_110]
+    msp_fpg: [1_330, 1_803.33]
+    msp_category: [QI, NONE]
+
+- name: Case 28, an undocumented spouse's income counts whether or not that spouse can enroll in Medicare.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 70
+        is_tax_unit_head: true
+        ssi_unearned_income: 12_000
+      person2:
+        age: 70
+        is_tax_unit_spouse: true
+        immigration_status: UNDOCUMENTED
+        ssi_unearned_income: 18_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # With both on Medicare the incomes combine. With person2 off Medicare, each
+    # spouse's income is above 497 and is deemed (20 CFR 416.1163(d)(2)). Either way:
+    # 1,000 + 1,500 - 20 = 2,480, above 135% of the two-person guideline:
+    # 1.35 x 1,803.33 = 2,434.50.
+    msp_countable_income: [2_480, 2_480]
+    msp_fpg: [1_803.33, 1_803.33]
+    msp_category: [NONE, NONE]
+
+- name: Case 29, Illinois gives one 25 dollar exemption to a spouse on Medicare who has no income.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_unearned_income: 21_900
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: IL
+  output:
+    # PM 15-04-03-a: person2's 1,825 is above 497 and is deemed: 1,825 - 25 = 1,800,
+    # at or below the two-person 1,803.33, so QMB. The SSI 20 would leave 1,805: SLMB.
+    # person2 is tested alone, since person1 has no income: 1,825 - 25 = 1,800.
+    msp_countable_income: [1_800, 1_800]
+    msp_fpg: [1_803.33, 1_330]
+    msp_category: [QMB, NONE]
+
+- name: Case 30, a minor's wages are not counted as a spouse's when marital units are omitted.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 70
+        social_security_retirement: 20_400
+      person2:
+        age: 16
+        employment_income_before_lsr: 10_000
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # Omitted marital units put both people in one default unit, but a parent and the
+    # child they claim are not spouses, so each is tested alone.
+    # person1: 1,700 - 20 = 1,680 against the one-person 1,330.
+    # 120% is 1,596 and 135% is 1,795.50, and that Social Security income is too high
+    # for Texas Medicaid as a parent, so QI.
+    # person2: (10,000 / 12 - 20 - 65) / 2 = 374.17.
+    msp_countable_income: [1_680, 374.17]
+    msp_fpg: [1_330, 1_330]
+    msp_category: [QI, NONE]
+
+- name: Case 31, a spouse's income exactly at the rate difference is not deemed.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 20_160
+      person2:
+        age: 50
+        is_tax_unit_spouse: true
+        ssi_unearned_income: 5_964
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # 20 CFR 416.1163(d)(1): person2's 5,964 / 12 = 497 is not above 1,491 - 994 = 497,
+    # so person1 is tested alone: 1,680 - 20 = 1,660 against the one-person 1,330.
+    # 120% is 1,596 and 135% is 1,795.50, so QI.
+    # person2 has person1's 1,680 deemed: 497 + 1,680 - 20 = 2,157.
+    msp_countable_income: [1_660, 2_157]
+    msp_fpg: [1_330, 1_803.33]
+    msp_category: [QI, NONE]
+
+- name: Case 32, a spouse's income one dollar above the rate difference is deemed.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 20_160
+      person2:
+        age: 50
+        is_tax_unit_spouse: true
+        ssi_unearned_income: 5_976
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # 20 CFR 416.1163(d)(2): person2's 5,976 / 12 = 498 is above 497, so it is deemed:
+    # 1,680 + 498 - 20 = 2,158 against the two-person 1,803.33.
+    # 120% is 2,164, so SLMB.
+    msp_countable_income: [2_158, 2_158]
+    msp_fpg: [1_803.33, 1_803.33]
+    msp_category: [SLMB, NONE]
+
+- name: Case 33, Illinois gives an eligible SSI couple one 25 dollar exemption when one spouse is on Medicare.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 1_200
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_unearned_income: 15_600
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: IL
+  output:
+    # 20 CFR 416.1801(c): 100 + 1,300 - 20 = 1,380 is below the 1,491 couple rate, so
+    # each spouse is eligible for SSI: (1,491 - 1,380) / 2 = 55.50.
+    # PM 15-04-03-a: only person1 applies, so one $25: 100 + 1,300 - 25 = 1,375.
+    # A $25 for each spouse would give 1,350.
+    uncapped_ssi: [55.50, 55.50]
+    msp_countable_income: [1_375, 1_375]
+    msp_fpg: [1_803.33, 1_803.33]
+    msp_category: [QMB, NONE]
diff --git a/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_fpg.yaml b/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_fpg.yaml
index 14acc4c3fb0..0ffd2931b33 100644
--- a/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_fpg.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/income/msp_fpg.yaml
@@ -12,11 +12,89 @@
     # Individual FPL = $15,060/year, monthly = $1,255
     msp_fpg: 1_255
 
-- name: Case 2, married couple gets couple FPL.
+- name: Case 2, married couple both on Medicare gets couple FPL.
   period: 2024-01
   absolute_error_margin: 0.01
   input:
-    spm_unit_is_married: true
+    people:
+      person1:
+        age: 68
+      person2:
+        age: 66
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
   output:
     # Couple FPL = $20,440/year, monthly = $1,703.33
-    msp_fpg: 1_703.33
+    msp_fpg: [1_703.33, 1_703.33]
+
+- name: Case 3, spouses separated by a facility each keep the one-person guideline.
+  period: 2026-01
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 12_000
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_lives_in_medical_treatment_facility: true
+        ssi_medicaid_pays_majority_of_care: true
+        ssi_unearned_income: 18_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+  output:
+    # 20 CFR 416.414(b)(3) computes the spouses separately, though each one's income
+    # is above the 497 rate difference. One-person guideline: 15,960 / 12 = 1,330.
+    msp_fpg: [1_330, 1_330]
+
+- name: Case 4, the guideline and income test change in the month a spouse enters a facility.
+  period: 2026
+  absolute_error_margin: 0.01
+  input:
+    people:
+      person1:
+        age: 68
+        is_tax_unit_head: true
+        ssi_unearned_income: 12_000
+      person2:
+        age: 62
+        is_tax_unit_spouse: true
+        meets_ssi_disability_criteria: true
+        ssi_lives_in_medical_treatment_facility:
+          2026-07: true
+        ssi_medicaid_pays_majority_of_care:
+          2026-07: true
+        ssi_unearned_income: 18_000
+    tax_units:
+      tax_unit:
+        members: [person1, person2]
+    marital_units:
+      marital_unit:
+        members: [person1, person2]
+    households:
+      household:
+        members: [person1, person2]
+        state_code: TX
+  output:
+    # June, both at home: each spouse's income is above 497 and is deemed:
+    # 1,000 + 1,500 - 20 = 2,480, above 1.35 x 21,640 / 12 = 2,434.50.
+    # July, person2 in a facility (20 CFR 416.414(b)(3)): each is tested alone.
+    # person1: 1,000 - 20 = 980, at or below 15,960 / 12 = 1,330, so QMB.
+    # person2: 1,500 - 20 = 1,480, and not on Medicare.
+    msp_fpg:
+      2026-06: [1_803.33, 1_803.33]
+      2026-07: [1_330, 1_330]
+    msp_countable_income:
+      2026-06: [2_480, 2_480]
+      2026-07: [980, 1_480]
+    msp_category:
+      2026-06: [NONE, NONE]
+      2026-07: [QMB, NONE]
diff --git a/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/integration.yaml b/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/integration.yaml
index c177b3f7b3a..fc59c8d7f50 100644
--- a/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/integration.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/integration.yaml
@@ -1,5 +1,6 @@
 # MSP uses SSI income methodology per 42 U.S.C. 1396d(p)(1)(B)
-# For married couples, MSP uses couple FPL = $20,440 for 2024
+# A married person tested as a couple (msp_tests_as_couple) uses the two-person
+# FPL = $20,440 for 2024; a married person tested alone uses the one-person FPL.
 
 - name: MSP integration - married couple, both QMB eligible
   period: 2024-01
@@ -111,8 +112,8 @@
   # Edge case: only one spouse is Medicare-eligible.
   # person.marital_unit.sum(is_medicare_eligible) == 1, not 2, so full couple
   # aggregation does not apply. With no spouse income to deem, spouse1 is
-  # tested on their own income ($10,000) against the married MSP threshold.
-  # ($10,000 - $240) / 12 = $813.33/month < $1,703.33 -> QMB.
+  # tested on their own income ($10,000) against the one-person guideline.
+  # ($10,000 - $240) / 12 = $813.33/month < $1,255 -> QMB.
   # Spouse2 is not Medicare-eligible and cannot qualify for MSP.
   input:
     people:
diff --git a/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/_msp_spouse_income.py b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/_msp_spouse_income.py
new file mode 100644
index 00000000000..d599a79bc19
--- /dev/null
+++ b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/_msp_spouse_income.py
@@ -0,0 +1,42 @@
+from policyengine_us.model_api import *
+
+
+def msp_spouse_value(values: ArrayLike, spouse: ArrayLike) -> ArrayLike:
+    # Each person's spouse's value, or zero for a person with no spouse. The
+    # spouse is the row from _ssi_spouse_index, not the rest of the marital unit,
+    # because a situation that omits marital units puts everyone in one.
+    return values[np.maximum(spouse, 0)] * (spouse >= 0)
+
+
+def msp_spouses_combine_income(
+    person: Population, period: Period, spouse: ArrayLike
+) -> ArrayLike:
+    # Spouses who are both on Medicare are tested together. So is an eligible
+    # couple: each spouse must be eligible for SSI (20 CFR 416.1801(c); POMS SI
+    # 00501.154 A.1), not only aged, blind or disabled, and uncapped_ssi above
+    # zero adds the income test that is_ssi_eligible leaves out.
+    is_medicare_eligible = person("is_medicare_eligible", period.this_year)
+    both_on_medicare = is_medicare_eligible & msp_spouse_value(
+        is_medicare_eligible, spouse
+    )
+    eligible_for_ssi = person("uncapped_ssi", period) > 0
+    eligible_couple = (
+        person("ssi_couple_computation_applies", period)
+        & eligible_for_ssi
+        & msp_spouse_value(eligible_for_ssi, spouse)
+    )
+    return both_on_medicare | eligible_couple
+
+
+def msp_spouse_income(person: Population, year: Period, spouse: ArrayLike) -> tuple:
+    # A spouse's annual earned and unearned income after allocations for
+    # ineligible children, which come off unearned income first (20 CFR
+    # 416.1163(a) and (b)). Any spouse who is not eligible for SSI is an
+    # ineligible spouse, whether or not aged, blind or disabled (20 CFR
+    # 416.1160(d)).
+    spouse_earned = msp_spouse_value(person("ssi_earned_income", year), spouse)
+    spouse_unearned = msp_spouse_value(person("ssi_unearned_income", year), spouse)
+    allocations = add(person.tax_unit, year, ["ssi_ineligible_child_allocation"])
+    earned_left = max_(spouse_earned - max_(allocations - spouse_unearned, 0), 0)
+    unearned_left = max_(spouse_unearned - allocations, 0)
+    return earned_left, unearned_left
diff --git a/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_countable_income.py b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_countable_income.py
index 99b10f12989..196ced94d51 100644
--- a/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_countable_income.py
+++ b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_countable_income.py
@@ -1,7 +1,15 @@
 from policyengine_us.model_api import *
+from policyengine_us.variables.gov.hhs.medicare.savings_programs.income._msp_spouse_income import (
+    msp_spouse_income,
+    msp_spouse_value,
+    msp_spouses_combine_income,
+)
 from policyengine_us.variables.gov.ssa.ssi.eligibility.income._apply_ssi_exclusions import (
     _apply_ssi_exclusions,
 )
+from policyengine_us.variables.gov.ssa.ssi.eligibility.resources.deemed._ssi_spouses import (
+    _ssi_spouse_index,
+)
 
 
 class msp_countable_income(Variable):
@@ -12,7 +20,12 @@ class msp_countable_income(Variable):
     definition_period = MONTH
     reference = (
         "https://www.law.cornell.edu/uscode/text/42/1396d#p",
+        "https://www.law.cornell.edu/cfr/text/20/416.412",
+        "https://www.law.cornell.edu/cfr/text/20/416.414",
+        "https://www.law.cornell.edu/cfr/text/20/416.1160",
         "https://www.law.cornell.edu/cfr/text/20/416.1163",
+        "https://www.law.cornell.edu/cfr/text/20/416.1801",
+        "https://secure.ssa.gov/poms.nsf/lnx/0500501154",
         "https://secure.ssa.gov/apps10/poms.nsf/lnx/0501715010",
         "https://www.medicare.gov/basics/costs/help/medicare-savings-programs",
         "https://www.law.cornell.edu/uscode/text/42/1396a#r_2",
@@ -27,27 +40,40 @@ class msp_countable_income(Variable):
     2. $65 earned income exclusion
     3. 50% of remaining earned income excluded
 
-    For married couples where both spouses are Medicare-eligible, SSI couple
-    rules apply per 20 CFR 416.1160: both spouses' incomes are combined before
-    exclusions are applied, and the $20 exclusion is taken once on the combined
-    income. The combined countable income is then compared against the couple FPL
-    in the eligibility variables (is_qmb_eligible, is_slmb_eligible, is_qi_eligible).
+    For married couples where both spouses are Medicare-eligible, or who are an
+    eligible couple because each is eligible for SSI (20 CFR 416.412 and
+    416.1801(c)), both spouses' incomes are combined before exclusions are
+    applied, and the $20 exclusion is taken once on the combined income.
+
+    Any other spouse is an ineligible spouse under 20 CFR 416.1160(d), even one
+    who is aged, blind or disabled. Under 20 CFR 416.1163, allocations for
+    ineligible children come off that spouse's income. A remainder above the
+    difference between the couple and individual benefit rates is added to the
+    person's own income before exclusions, and otherwise nothing is deemed. A
+    medical treatment facility that separates a couple leaves each with their own
+    income (20 CFR 416.414(b)(3)). The eligibility variables (is_qmb_eligible,
+    is_slmb_eligible, is_qi_eligible) compare the result with msp_fpg, which is the
+    couple FPL whenever msp_tests_as_couple is true.
 
     Under 42 U.S.C. 1396a(r)(2) a state may exclude more than the $20 SSI
     general income exclusion; Illinois and Mississippi use their larger
     exclusion in its place. Mississippi takes it once from a couple's
     combined income; Illinois gives each applying spouse with income their
-    own exclusion, up to that spouse's income. Illinois gives its $25 only on
-    income other than SSI and contributions (alimony, child support, outside
-    cash help); the $20 SSI exclusion stays the floor.
+    own exclusion, up to that spouse's income, and one exclusion when only one
+    spouse is on Medicare. Illinois gives its $25 only on income other than SSI
+    and contributions (alimony, child support, outside cash help); the $20 SSI
+    exclusion stays the floor.
     """
 
     def formula(person, period, parameters):
         year = period.this_year
         earned_income = person("ssi_earned_income", year)
         unearned_income = person("ssi_unearned_income", year)
+        spouse = _ssi_spouse_index(person, year)
         is_medicare_eligible = person("is_medicare_eligible", year)
-        both_medicare_eligible = person.marital_unit.sum(is_medicare_eligible) == 2
+        both_medicare_eligible = is_medicare_eligible & msp_spouse_value(
+            is_medicare_eligible, spouse
+        )
 
         blind_or_disabled_working_student_exclusion = person(
             "ssi_blind_or_disabled_working_student_exclusion", year
@@ -56,7 +82,6 @@ def formula(person, period, parameters):
             earned_income - blind_or_disabled_working_student_exclusion,
             0,
         )
-        deeming_applies = person("is_ssi_spousal_deeming_applies", year)
         state = person.household("state_code_str", period)
         p = parameters(period).gov.hhs.medicare.savings_programs.eligibility.income
         ssi_general = parameters(period).gov.ssa.ssi.income.exclusions.general
@@ -86,21 +111,22 @@ def formula(person, period, parameters):
             max_(ssi_general, min_(state_exclusion, qualifying_income)),
             general_exclusion,
         )
+        # Two spouses on Medicare each apply. When only one does, PM 15-04-03-a
+        # allows one $25 on income in the standard, even if that spouse has no
+        # income other than SSI or contributions.
         per_spouse = p.state_general_exclusion_per_spouse[state].astype(bool)
+        own_exemption = min_(state_exclusion, qualifying_income)
         couple_general_exclusion = where(
-            per_spouse,
+            per_spouse & both_medicare_eligible,
             max_(
                 ssi_general,
-                person.marital_unit.sum(min_(state_exclusion, qualifying_income)),
+                own_exemption + msp_spouse_value(own_exemption, spouse),
             ),
             general_exclusion,
         )
 
-        spouse_earned_income = person(
-            "ssi_earned_income_deemed_from_ineligible_spouse", year
-        )
-        spouse_unearned_income = person(
-            "ssi_unearned_income_deemed_from_ineligible_spouse", year
+        spouse_earned_income, spouse_unearned_income = msp_spouse_income(
+            person, year, spouse
         )
         personal_countable_income = _apply_ssi_exclusions(
             personal_earned_income,
@@ -112,11 +138,13 @@ def formula(person, period, parameters):
 
         couple_countable = _apply_ssi_exclusions(
             max_(
-                person.marital_unit.sum(earned_income)
-                - person.marital_unit.sum(blind_or_disabled_working_student_exclusion),
+                earned_income
+                + msp_spouse_value(earned_income, spouse)
+                - blind_or_disabled_working_student_exclusion
+                - msp_spouse_value(blind_or_disabled_working_student_exclusion, spouse),
                 0,
             ),
-            person.marital_unit.sum(unearned_income),
+            unearned_income + msp_spouse_value(unearned_income, spouse),
             parameters,
             year,
             general_exclusion=couple_general_exclusion,
@@ -131,10 +159,14 @@ def formula(person, period, parameters):
         )
 
         single_countable = where(
-            deeming_applies, deemed_countable, personal_countable_income
+            person("msp_tests_as_couple", period),
+            deemed_countable,
+            personal_countable_income,
         )
 
         annual_countable = where(
-            both_medicare_eligible, couple_countable, single_countable
+            msp_spouses_combine_income(person, period, spouse),
+            couple_countable,
+            single_countable,
         )
         return annual_countable / MONTHS_IN_YEAR
diff --git a/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_fpg.py b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_fpg.py
index b1cb24efc20..be47fb61f66 100644
--- a/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_fpg.py
+++ b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_fpg.py
@@ -6,16 +6,18 @@ class msp_fpg(Variable):
     entity = Person
     unit = USD
     label = "MSP Federal Poverty Guideline"
-    definition_period = YEAR
+    definition_period = MONTH
     reference = (
         "https://www.law.cornell.edu/uscode/text/42/1396d#p",
+        "https://www.law.cornell.edu/cfr/text/20/416.1163",
         "https://www.medicare.gov/basics/costs/help/medicare-savings-programs",
     )
     documentation = """
-    The Federal Poverty Guideline used for MSP eligibility is based on
+    The monthly Federal Poverty Guideline used for MSP eligibility is based on
     individual or couple status, not the full household/SPM unit size.
     Per 42 U.S.C. 1396d(p), MSP income limits are based on the federal
-    poverty line for a family of the size involved.
+    poverty line for a family of the size involved. The family is two people
+    when msp_tests_as_couple is true, and one otherwise.
 
     Note: Published Medicare.gov limits are $20/month higher than raw FPL
     because they include the $20 general income exclusion in the threshold.
@@ -29,12 +31,11 @@ def formula(person, period, parameters):
         # Note: These are raw FPL values. Published limits are $20 higher
         # because we apply the $20 exclusion to income (msp_countable_income)
         # rather than adding it to the threshold.
-        married = person.spm_unit("spm_unit_is_married", period.this_year)
+        tests_as_couple = person("msp_tests_as_couple", period)
         state_group = person.household("state_group_str", period)
         p = parameters(period).gov.hhs.fpg
         p1 = p.first_person[state_group]
         pn = p.additional_person[state_group]
-        # 1 person if single, 2 persons if married
         individual_fpg = p1
         couple_fpg = p1 + pn
-        return where(married, couple_fpg, individual_fpg)
+        return where(tests_as_couple, couple_fpg, individual_fpg) / MONTHS_IN_YEAR
diff --git a/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_tests_as_couple.py b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_tests_as_couple.py
new file mode 100644
index 00000000000..e5c72cec3a1
--- /dev/null
+++ b/policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_tests_as_couple.py
@@ -0,0 +1,48 @@
+from policyengine_us.model_api import *
+from policyengine_us.variables.gov.hhs.medicare.savings_programs.income._msp_spouse_income import (
+    msp_spouse_income,
+    msp_spouses_combine_income,
+)
+from policyengine_us.variables.gov.ssa.ssi.eligibility.resources.deemed._ssi_spouses import (
+    _ssi_spouse_index,
+)
+
+
+class msp_tests_as_couple(Variable):
+    value_type = bool
+    entity = Person
+    label = "Medicare Savings Program tests this person as a couple"
+    definition_period = MONTH
+    reference = (
+        "https://www.law.cornell.edu/uscode/text/42/1396d#p",
+        "https://www.law.cornell.edu/cfr/text/20/416.414",
+        "https://www.law.cornell.edu/cfr/text/20/416.1160",
+        "https://www.law.cornell.edu/cfr/text/20/416.1163",
+        "https://www.law.cornell.edu/cfr/text/20/416.1801",
+        "https://secure.ssa.gov/poms.nsf/lnx/0500501154",
+    )
+    documentation = """
+    Whether SSI's spouse rules count a spouse's income for this person, which also
+    makes the two-person poverty guideline the income limit. That holds when both
+    spouses are on Medicare, when they are an eligible couple, or when the spouse's
+    income after allocations for ineligible children is more than the difference
+    between the couple and individual benefit rates (20 CFR 416.1163(d)(2)). If it
+    is not more, nothing is deemed (416.1163(d)(1)). A medical treatment facility
+    that separates a couple also leaves each spouse tested alone (416.414(b)(3)),
+    unless both are on Medicare, when the model still tests them together. A person
+    with no co-resident spouse (_ssi_spouse_index) is always tested alone.
+    """
+
+    def formula(person, period, parameters):
+        year = period.this_year
+        spouse = _ssi_spouse_index(person, year)
+        spouse_earned, spouse_unearned = msp_spouse_income(person, year, spouse)
+        p = parameters(period).gov.ssa.ssi.amount
+        rate_difference = (p.couple - p.individual) * MONTHS_IN_YEAR
+        spouse_income_is_deemed = spouse_earned + spouse_unearned > rate_difference
+        split_by_facility = person("ssi_claim_is_joint", year) & ~person(
+            "ssi_couple_computation_applies", period
+        )
+        return msp_spouses_combine_income(person, period, spouse) | (
+            spouse_income_is_deemed & ~split_by_facility
+        )
diff --git a/source_conflicts/candidates.yaml b/source_conflicts/candidates.yaml
index 02d04ed6e37..41303e1c9e6 100644
--- a/source_conflicts/candidates.yaml
+++ b/source_conflicts/candidates.yaml
@@ -2779,6 +2779,43 @@ candidates:
   state: ruled
   note: Ruled statute-first in October 2026; verify the incorporated dependency bar and annual questionnaire routing,
     including the 2026 draft.
+- id: us-il:msp-exemption-applicant-without-income
+  program: medicare-savings-programs
+  years:
+    from: 2026
+    type: calendar
+  question: Does an Illinois Medicare Savings Program applicant with no income of their own get the $25 exemption on
+    income counted from a spouse who is not applying?
+  sources:
+  - kind: manual
+    citation: IDHS Policy Manual PM 15-04-03-a
+    url: https://www.dhs.state.il.us/page.aspx?item=16387
+  - kind: regulation
+    citation: 89 Ill. Adm. Code 120.335(a)(1)
+    url: https://www.ilga.gov/ftp/JCAR/AdminCode/089/089001200H03350R.html
+  - kind: manual
+    citation: IDHS Policy Manual PM 06-12-01-c
+    url: https://www.dhs.state.il.us/page.aspx?item=14179
+  readings:
+    statute: 'No statute is supplied; 120.335(a)(1) exempts "the first $25.00 of a client''s earned or unearned income
+      other than SSI income, or contributions from a spouse or other individual", and PM 06-12-01-c allows "no more
+      than one income exemption for their own income" and an exemption on a spouse''s income only if the spouse "is
+      an applicant or client in another MANG case".'
+    other: 'PM 15-04-03-a: "If the person applying for or receiving AABD Medical has no income other than SSI or
+      contributions, and another person included in the standard has income, deduct one $25 exemption even if the
+      other person receives benefits under one of the Family Health Plans."'
+  example: An Illinois applicant, 68, with no income and a disabled spouse, 62, with $1,825 a month counts $1,800 and
+    is QMB with one $25, and counts $1,805 and is SLMB with only the SSI $20.
+  pe_us:
+    follows: conflicting-source
+    code:
+    - policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_countable_income.py
+    prs:
+    - https://github.com/PolicyEngine/policyengine-us/pull/10633
+  state: ruled
+  note: 'PE-US follows PM 15-04-03-a: one $25 applies when only one spouse is on Medicare, whether or not that spouse
+    has income of their own. Two spouses on Medicare keep one exemption each, capped at each spouse''s own income. Ruled
+    by the project lead, 2026-11-02: https://github.com/PolicyEngine/policyengine-us/pull/10633'
 - id: us-il:msp-income-exemption-contributions
   program: medicare-savings-programs
   years:
@@ -10580,6 +10617,52 @@ candidates:
     three places, and floors the result at the federal deduction, a PE safeguard that binds only when the rounded
     share falls below the exact federal share. Settling the federal reading (rulespec-us#1413) and using it for
     both would make that floor unnecessary.'
+- id: us:msp-eligible-spouse-ssi-definition
+  program: medicare-savings-programs
+  years:
+    from: 2026
+    type: calendar
+  question: Under SSI methodology for the Medicare Savings Programs, is a spouse who is aged, blind or disabled but not
+    eligible for SSI an eligible spouse, whose income is combined, or an ineligible spouse, whose income is deemed?
+  sources:
+  - kind: statute
+    citation: 42 U.S.C. 1382c(b) and (f)(1)
+    url: https://www.law.cornell.edu/uscode/text/42/1382c
+  - kind: regulation
+    citation: 20 CFR 416.1801(c)
+    url: https://www.law.cornell.edu/cfr/text/20/416.1801
+  - kind: regulation
+    citation: 20 CFR 416.1160(d)
+    url: https://www.law.cornell.edu/cfr/text/20/416.1160
+  - kind: regulation
+    citation: 20 CFR 416.1163(b) and (d)
+    url: https://www.law.cornell.edu/cfr/text/20/416.1163
+  - kind: manual
+    citation: POMS SI 00501.154 A.1
+    url: https://secure.ssa.gov/poms.nsf/lnx/0500501154
+  readings:
+    statute: 'Section 1382c(b) defines an eligible spouse as "an aged, blind, or disabled individual" married to and
+      living with another such individual, and (f)(1) deems income from a spouse who "is not an eligible spouse".'
+    other: '416.1801(c) defines an eligible spouse as a person "Who is eligible for SSI"; 416.1160(d) defines an
+      ineligible spouse as someone who "is not eligible for SSI benefits"; POMS SI 00501.154 A.1 applies couple
+      computation rules if "each is eligible for benefits". 416.1163 then allocates to ineligible children and deems
+      only a remainder above the rate difference.'
+  example: A, on Medicare, has $1,000 a month and B, 62 and disabled, has $1,500, with two ineligible children. Combined
+    income is $2,480 and no tier; under deeming it is $1,000 + ($1,500 - 2 x $497) - $20 = $1,486 and QMB.
+  pe_us:
+    follows: conflicting-source
+    code:
+    - policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_tests_as_couple.py
+    - policyengine_us/variables/gov/hhs/medicare/savings_programs/income/_msp_spouse_income.py
+    - policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_countable_income.py
+    - policyengine_us/variables/gov/hhs/medicare/savings_programs/income/msp_fpg.py
+    prs:
+    - https://github.com/PolicyEngine/policyengine-us/pull/10633
+  state: ruled
+  note: 'PE-US follows the regulations for the Medicare Savings Programs: spouses are an eligible couple only if each
+    is eligible for SSI, and any other spouse is an ineligible spouse, with income deemed above the rate difference.
+    The SSI variables (is_ssi_ineligible_spouse, ssi_couple_computation_applies) still classify by aged, blind or
+    disabled status. Ruled by the project lead, 2026-11-02: https://github.com/PolicyEngine/policyengine-us/pull/10633'
 - id: us:niit-excess-business-loss-addback
   program: income-tax
   years: