DTrim99 · Nov 6, 2026 · Nov 7, 2026 · Nov 7, 2026 · Nov 9, 2026
diff --git a/changelog.d/irs-2027-indexing.changed.md b/changelog.d/irs-2027-indexing.changed.md
@@ -0,0 +1 @@
+Update federal tax parameters to the IRS's 2027 inflation-adjusted amounts in Rev. Proc. 2026-35: income tax brackets, capital gains thresholds, standard deductions, the EITC, the child tax credit's refundable amount, the AMT, the QBI deduction, and other indexed amounts, plus Arizona's standard deduction and Maine's aged or blind addition, which follow the federal amounts.
diff --git a/policyengine_us/parameters/gov/irs/ald/educator_expense/cap.yaml b/policyengine_us/parameters/gov/irs/ald/educator_expense/cap.yaml
@@ -15,6 +15,7 @@ values:
   2024-01-01: 300
   2025-01-01: 300
   2026-01-01: 350
+  2027-01-01: 350
 metadata:
   unit: currency-USD
   period: year
@@ -57,5 +58,7 @@ metadata:
       href: https://www.irs.gov/pub/irs-drop/rp-23-34.pdf#page=11
     - title: Rev. Proc. 2024-40, section 2.13 (2025)
       href: https://www.irs.gov/pub/irs-drop/rp-24-40.pdf#page=11
+    - title: Rev. Proc. 2026-35, section 3.13 (2027)
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=12
     - title: Rev. Proc. 2025-32, section 4.12 (2026)
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=17
diff --git a/policyengine_us/parameters/gov/irs/ald/loss/max.yaml b/policyengine_us/parameters/gov/irs/ald/loss/max.yaml
@@ -15,6 +15,8 @@ metadata:
       href: https://www.congress.gov/bill/119th-congress/house-bill/1/text
     - title: 2025 Form 461, line 15
       href: https://www.irs.gov/pub/irs-prior/f461--2025.pdf
+    - title: Revenue Procedure 2026-35, section 3.33 (2027 threshold)
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=19
     - title: Revenue Procedure 2025-32, section 4.31 (2026 threshold)
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=23
     - title: 2024 IRS data release
@@ -44,6 +46,7 @@ HEAD_OF_HOUSEHOLD:
     2024-01-01: 305_000
     2025-01-01: 313_000
     2026-01-01: 256_000
+    2027-01-01: 264_000
 JOINT:
   metadata:
     uprating:
@@ -61,6 +64,7 @@ JOINT:
     2024-01-01: 610_000
     2025-01-01: 626_000
     2026-01-01: 512_000
+    2027-01-01: 528_000
 SEPARATE:
   metadata:
     uprating:
@@ -78,6 +82,7 @@ SEPARATE:
     2024-01-01: 305_000
     2025-01-01: 313_000
     2026-01-01: 256_000
+    2027-01-01: 264_000
 SINGLE:
   metadata:
     uprating:
@@ -95,6 +100,7 @@ SINGLE:
     2024-01-01: 305_000
     2025-01-01: 313_000
     2026-01-01: 256_000
+    2027-01-01: 264_000
 SURVIVING_SPOUSE:
   metadata:
     uprating:
@@ -113,3 +119,4 @@ SURVIVING_SPOUSE:
     2024-01-01: 305_000
     2025-01-01: 313_000
     2026-01-01: 256_000
+    2027-01-01: 264_000
diff --git a/policyengine_us/parameters/gov/irs/ald/student_loan_interest/reduction/start.yaml b/policyengine_us/parameters/gov/irs/ald/student_loan_interest/reduction/start.yaml
@@ -10,6 +10,8 @@ metadata:
   reference:
     - title: 26 U.S. Code § 221 - Interest on education loans (b)(1)
       href: https://www.law.cornell.edu/uscode/text/26/221
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=18
     - title: 2026 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=23
     - title: 2023 IRS data release
@@ -34,6 +36,7 @@ JOINT:
     2024-01-01: 165_000
     2025-01-01: 170_000
     2026-01-01: 175_000
+    2027-01-01: 180_000
   metadata:
     uprating:
       parameter: gov.irs.uprating
@@ -48,6 +51,7 @@ SINGLE:
     2024-01-01: 80_000
     2025-01-01: 85_000
     2026-01-01: 85_000
+    2027-01-01: 90_000
   metadata:
     uprating:
       parameter: gov.irs.uprating
@@ -65,6 +69,7 @@ HEAD_OF_HOUSEHOLD:
     2024-01-01: 80_000
     2025-01-01: 85_000
     2026-01-01: 85_000
+    2027-01-01: 90_000
   metadata:
     uprating:
       parameter: gov.irs.uprating
@@ -79,6 +84,7 @@ SURVIVING_SPOUSE:
     2024-01-01: 80_000
     2025-01-01: 85_000
     2026-01-01: 85_000
+    2027-01-01: 90_000
   metadata:
     uprating:
       parameter: gov.irs.uprating

diff --git a/policyengine_us/parameters/gov/irs/capital_gains/thresholds.yaml b/policyengine_us/parameters/gov/irs/capital_gains/thresholds.yaml
@@ -15,6 +15,8 @@ metadata:
   reference:
     - title: 26 U.S. Code § 1(j)(5)(B) - Capital gains rate thresholds
       href: https://www.law.cornell.edu/uscode/text/26/1#j_5_B
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=7
     - title: 2026 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=13
     - title: 2025 IRS data release
@@ -47,6 +49,7 @@ metadata:
     2024-01-01: 63_000
     2025-01-01: 64_750
     2026-01-01: 66_200
+    2027-01-01: 68_350
   JOINT:
     2013-01-01: 72_500
     2014-01-01: 73_800
@@ -62,6 +65,7 @@ metadata:
     2024-01-01: 94_050
     2025-01-01: 96_700
     2026-01-01: 98_900
+    2027-01-01: 102_100
   SEPARATE:
     2013-01-01: 36_250
     2014-01-01: 36_900
@@ -77,6 +81,7 @@ metadata:
     2024-01-01: 47_025
     2025-01-01: 48_350
     2026-01-01: 49_450
+    2027-01-01: 51_050
   SINGLE:
     2013-01-01: 36_250
     2014-01-01: 36_900
@@ -92,6 +97,7 @@ metadata:
     2024-01-01: 47_025
     2025-01-01: 48_350
     2026-01-01: 49_450
+    2027-01-01: 51_050
   SURVIVING_SPOUSE:
     2013-01-01: 72_500
     2014-01-01: 73_800
@@ -107,6 +113,7 @@ metadata:
     2024-01-01: 94_050
     2025-01-01: 96_700
     2026-01-01: 98_900
+    2027-01-01: 102_100
 2:
   HEAD_OF_HOUSEHOLD:
     2013-01-01: 425_000
@@ -123,6 +130,7 @@ metadata:
     2024-01-01: 551_350
     2025-01-01: 566_700
     2026-01-01: 579_600
+    2027-01-01: 598_400
   JOINT:
     2013-01-01: 450_000
     2014-01-01: 457_600
@@ -138,6 +146,7 @@ metadata:
     2024-01-01: 583_750
     2025-01-01: 600_050
     2026-01-01: 613_700
+    2027-01-01: 633_600
   SEPARATE:
     2013-01-01: 225_000
     2014-01-01: 228_800
@@ -153,6 +162,7 @@ metadata:
     2024-01-01: 291_850
     2025-01-01: 300_000
     2026-01-01: 306_850
+    2027-01-01: 316_800
   SINGLE:
     2013-01-01: 400_000
     2014-01-01: 406_750
@@ -168,6 +178,7 @@ metadata:
     2024-01-01: 518_900
     2025-01-01: 533_400
     2026-01-01: 545_500
+    2027-01-01: 563_200
   SURVIVING_SPOUSE:
     2013-01-01: 450_000
     2014-01-01: 457_600
@@ -183,3 +194,4 @@ metadata:
     2024-01-01: 583_750
     2025-01-01: 600_050
     2026-01-01: 613_700
+    2027-01-01: 633_600
diff --git a/policyengine_us/parameters/gov/irs/credits/ctc/amount/base.yaml b/policyengine_us/parameters/gov/irs/credits/ctc/amount/base.yaml
@@ -26,6 +26,8 @@ brackets:
             href: https://www.law.cornell.edu/uscode/text/26/24#h_2
           - title: 26 U.S. Code § 24(i)(2) - Inflation adjustment for credit amount
             href: https://www.law.cornell.edu/uscode/text/26/24#i_2
+          - title: 2027 IRS data release
+            href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=8
           - title: 2026 IRS data release
             href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=14
         # IRC §24(i)(2) adjusts the $2,200 statutory base using 2024 as reference year.

diff --git a/policyengine_us/parameters/gov/irs/credits/ctc/refundable/individual_max.yaml b/policyengine_us/parameters/gov/irs/credits/ctc/refundable/individual_max.yaml
@@ -11,8 +11,8 @@ values:
   # law (the statutory cap has not been indexed high enough to round up).
   2025-01-01: 1_700
   2026-01-01: 1_700
-  # CBO forecast.
   2027-01-01: 1_800
+  # CBO forecast.
   2029-01-01: 1_900
   2032-01-01: 2_000
   2034-01-01: 2_100
@@ -30,6 +30,8 @@ metadata:
       href: https://www.law.cornell.edu/uscode/text/26/24#h_5_A
     - title: 26 U.S. Code § 24(i)(1) - Inflation adjustment for refundable amount
       href: https://www.law.cornell.edu/uscode/text/26/24#i_1
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=8
     - title: 2026 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=14
     - title: 2025 IRS data release

diff --git a/policyengine_us/parameters/gov/irs/credits/eitc/max.yaml b/policyengine_us/parameters/gov/irs/credits/eitc/max.yaml
@@ -15,6 +15,7 @@ brackets:
         2024-01-01: 632
         2025-01-01: 649
         2026-01-01: 664
+        2027-01-01: 685
       metadata:
         uprating:
           parameter: gov.irs.uprating
@@ -35,6 +36,7 @@ brackets:
         2024-01-01: 4_213
         2025-01-01: 4_328
         2026-01-01: 4_427
+        2027-01-01: 4_573
       metadata:
         uprating:
           parameter: gov.irs.uprating
@@ -55,6 +57,7 @@ brackets:
         2024-01-01: 6_960
         2025-01-01: 7_152
         2026-01-01: 7_316
+        2027-01-01: 7_552
       metadata:
         uprating:
           parameter: gov.irs.uprating
@@ -75,6 +78,7 @@ brackets:
         2024-01-01: 7_830
         2025-01-01: 8_046
         2026-01-01: 8_231
+        2027-01-01: 8_496
       metadata:
         uprating:
           parameter: gov.irs.uprating
@@ -90,6 +94,8 @@ metadata:
     - title: 26 U.S.C. § 32(b) - Earned Income Credit
       href: https://www.law.cornell.edu/uscode/text/26/32#b
       # Defines EITC percentages and maximum amounts by number of children
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=10
     - title: 2026 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=14
     - title: 2025 IRS data release

diff --git a/policyengine_us/parameters/gov/irs/credits/eitc/phase_out/joint_bonus.yaml b/policyengine_us/parameters/gov/irs/credits/eitc/phase_out/joint_bonus.yaml
@@ -10,6 +10,8 @@ metadata:
     # Row 3: Threshold Phaseout Amount (Single, Surviving Spouse, or Head of
     #        Household), and
     # Row 5: Threshold Phaseout Amount (Married Filing Jointly)
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=10
     - title: 2026 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=15
     - title: 2025 IRS data release
@@ -59,8 +61,8 @@ brackets:
         2024-01-01: 6_920 # 17_250 - 10_330 
         2025-01-01: 7_110 # 17_730 - 10_620
         2026-01-01: 7_280 # 18_140 - 10_860
+        2027-01-01: 7_520 # 18_730 - 11_210
         # CBO forecast.
-        2027-01-01: 7_410
         2028-01-01: 7_570
         2029-01-01: 7_710
         2030-01-01: 7_870
@@ -98,8 +100,8 @@ brackets:
         2024-01-01: 6_920 # 29_640 - 22_720
         2025-01-01: 7_120 # 30_470 - 23_350
         2026-01-01: 7_270 # 31_160 - 23_890
+        2027-01-01: 7_510 # 32_170 - 24_660
         # CBO forecast.
-        2027-01-01: 7_420
         2028-01-01: 7_570
         2029-01-01: 7_720
         2030-01-01: 7_870

diff --git a/policyengine_us/parameters/gov/irs/credits/eitc/phase_out/max_investment_income.yaml b/policyengine_us/parameters/gov/irs/credits/eitc/phase_out/max_investment_income.yaml
@@ -5,6 +5,8 @@ metadata:
   label: EITC maximum investment income
   uprating: gov.irs.uprating
   reference:
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=10
     - title: 2026 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=15
     - title: 2025 IRS data release
@@ -36,3 +38,4 @@ values:
   2024-01-01: 11_600
   2025-01-01: 11_950
   2026-01-01: 12_200
+  2027-01-01: 12_600
diff --git a/policyengine_us/parameters/gov/irs/credits/eitc/phase_out/start.yaml b/policyengine_us/parameters/gov/irs/credits/eitc/phase_out/start.yaml
@@ -5,6 +5,8 @@ metadata:
   amount_unit: currency-USD
   label: EITC phase-out start by number of children
   reference:
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=10
     - title: 2026 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-25-32.pdf#page=15
     - title: 2025 IRS data release
@@ -57,8 +59,8 @@ brackets:
         2024-01-01: 10_330
         2025-01-01: 10_620
         2026-01-01: 10_860
+        2027-01-01: 11_210
         # CBO forecast.
-        2027-01-01: 11_070
         2028-01-01: 11_290
         2029-01-01: 11_520
         2030-01-01: 11_740
@@ -86,8 +88,8 @@ brackets:
         2024-01-01: 22_720
         2025-01-01: 23_350
         2026-01-01: 23_890
+        2027-01-01: 24_660
         # CBO forecast.
-        2027-01-01: 24_340
         2028-01-01: 24_830
         2029-01-01: 25_320
         2030-01-01: 25_820
@@ -115,8 +117,8 @@ brackets:
         2024-01-01: 22_720
         2025-01-01: 23_350
         2026-01-01: 23_890
+        2027-01-01: 24_660
         # CBO forecast.
-        2027-01-01: 24_340
         2028-01-01: 24_830
         2029-01-01: 25_320
         2030-01-01: 25_820
@@ -144,8 +146,8 @@ brackets:
         2024-01-01: 22_720
         2025-01-01: 23_350
         2026-01-01: 23_890
+        2027-01-01: 24_660
         # CBO forecast.
-        2027-01-01: 24_340
         2028-01-01: 24_830
         2029-01-01: 25_320
         2030-01-01: 25_820

diff --git a/policyengine_us/parameters/gov/irs/credits/estate/base.yaml b/policyengine_us/parameters/gov/irs/credits/estate/base.yaml
@@ -6,6 +6,8 @@ metadata:
   reference:
     - title: H.R.1 - One Big Beautiful Bill Act
       href: https://www.congress.gov/bill/119th-congress/house-bill/1/text
+    - title: 2027 IRS data release
+      href: https://www.irs.gov/pub/irs-drop/rp-26-35.pdf#page=21
     - title: 2025 IRS data release
       href: https://www.irs.gov/pub/irs-drop/rp-24-40.pdf#page=18
     - title: 26 U.S. Code § 2010 - Unified credit against estate tax - (c)(3)(A)
@@ -61,3 +63,4 @@ values:
   2025-01-01: 13_990_000
   # OBBBA sets the basic exclusion amount to $15M.
   2026-01-01: 15_000_000
+  2027-01-01: 15_480_000
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Update federal tax parameters to the IRS's 2027 inflation-adjusted amounts in Rev. Proc. 2026-35: income tax brackets, capital gains thresholds, standard deductions, the EITC, the child tax credit's refundable amount, the AMT, the QBI deduction, and other indexed amounts, plus Arizona's standard deduction and Maine's aged or blind addition, which follow the federal amounts.