Riverside GR: confirm payroll withholding scope and missing federal income tax deduction #10233

Problem

#9901 stops projecting tax-unit deductions onto every Riverside County General Relief member. Two pre-existing issues remain in the person-level wage-deduction measure: it omits federal income tax withholding and estimates California income withholding from the person's whole AGI rather than only employer-withheld tax on earnings.

policyengine_us/parameters/gov/local/ca/riv/general_relief/income/deductions/sources.yaml includes ca_withheld_income_tax, Social Security, Medicare, Additional Medicare withholding and traditional IRA contributions. It has no federal income tax withholding source. No person-level federal income tax withholding variable is currently available for that list.

ca_withheld_income_tax applies the California tax schedule to adjusted_gross_income_person. It therefore estimates withholding attributable to pension or interest income as well as wages. Keeping that amount with the same person fixes attribution but still deducts non-wage withholding from earned income. This follow-up focuses on federal withholding and employer-withheld earnings scope.

Sources and blocker

The contributor summary linked from #6252, under allowable deductions from earned income (DP 90-001 page 20), includes:

Federal, state, and local taxes

Summary: https://docs.google.com/document/d/1ht5Cz4flMIj2DE2soC6ir3e0s3hQ7l7DfVxW7zaPM7o/edit. It also paraphrases Social Security/Medicare, retirement, insurance premiums and mandatory payroll deductions. This is not verbatim county-manual text. The embedded original manual https://drive.google.com/file/d/13pJluJb86RlUo225qJBaTjqkEyM6k0C7/view redirected to Google sign-in on 2026-10-14.

Alameda County's General Assistance Handbook 90-05.151 page 3 expressly limits payroll deductions to amounts:

when deducted from the gross earnings by the employer

Official source: https://socialservices.alamedacountyca.gov/acssa-assets/PDF/GA-Policies/GA_Handbook_90-05.151.pdf#page=3 (last revised 2011-08-23). This corroborates why payroll withholding and tax liability are different concepts; it does not establish Riverside's law. Obtain Riverside DP 90-001 page 20 through TheAxiomFoundation/axiom-corpus#889 before changing county policy.

Concrete cases to pin after source confirmation

• Wage earner with $400/month of gross earnings, $30.60/month of employee Social Security/Medicare and $20/month of actual federal employer withholding, with zero other deductions: current represented payroll sources deduct $30.60 and leave $369.40; including allowable federal withholding would deduct $50.60 and leave $349.40. The $20 is an explicit withholding input, not an estimate of annual federal tax liability. Use a source-supported or actual-withholding input concept for the regression.
• A single person has $400/month of wages plus a $2,500/month pension. The current CA estimate can include pension withholding in the wage deduction. Hold the wage-payroll inputs fixed while changing pension/interest withholding; if the Riverside manual limits deductions to earnings withheld by the employer, only the relevant wage withholding belongs in the earned-income calculation. Do not set a final Riverside expected amount from Alameda's rule.
• Two earners: each person's federal and state wage withholding must stay with that earner; changing one earner's employer withholding must leave the other's deduction unchanged.
• Zero federal withholding despite positive year-end federal tax liability, and positive withholding despite zero final liability: use actual withholding in both, rather than substituting income_tax or another tax-unit liability.

Acceptance criteria

1. Obtain and quote authoritative DP 90-001 page 20, including which tax/payroll deductions are allowable and whether they must be withheld from earned income.
2. Define a person-level federal income withholding concept suitable for GR (actual employer withholding input or a documented approximation), including periods and employer aggregation. Do not project a tax-unit liability.
3. Restrict the state and federal deduction sources to the manual's confirmed earned-income scope. If an approximation is retained, document its pension/interest limitations visibly.
4. Add source-derived regressions for federal withholding, mixed wage/unearned income, and two earners. Keep Stop projecting group amounts onto every Riverside General Relief member #9901's attribution regressions and Additional Medicare preservation guard intact.
5. Extend the deferred deductions portion of Queue Riverside County GR combined-property parity for PolicyEngine/policyengine-us#9901 TheAxiomFoundation/rulespec-us#1774 only after the manual is ingested and the signed encoder can bind its source.

Related: #9901 and #6252. #9837 concerns the same state-withholding estimate in the federal SALT term; it does not cover Riverside's earned-income scope or its missing federal payroll withholding. Riverside title searches found no existing open deductions issue on 2026-10-15.