South Carolina TANF counts taxable UC and taxable Social Security instead of gross amounts #9677

Title: South Carolina TANF should count gross unemployment compensation and gross Social Security as unearned income

Problem

policyengine_us/parameters/gov/states/sc/tanf/income/unearned.yaml lists:

• line 17: taxable_unemployment_compensation
• line 18: taxable_social_security

The SC DSS TANF Policy Manual's Sources of Income chart (Volume 65, Section 7) counts unemployment compensation and SSA benefits as unearned income in full. It makes no carve-out for the federally taxable share. Using the taxable variables undercounts income in two ways:

• UC (tax year 2020 only). The §85(c) exclusion made up to $10,200 of 2020 UC tax-exempt, so SC TANF ignores that UC. For a parent and child with $6,000 a year of UC in 2020, sc_tanf is $237.59 a month. It would be $68.99 if gross UC counted (figures from the Integrate modeled state unemployment insurance into income flows #9558 review).
• Social Security (every year). taxable_social_security is 0 to 85% of benefits, depending on the tax unit's provisional income. Low-income TANF households usually have $0 taxable, so SC TANF counts none of their SSA benefits.

Proposed fix

1. Replace taxable_unemployment_compensation with total_unemployment_compensation. This is the gross amount: reported UC, or modeled state UI when none is reported (Integrate modeled state unemployment insurance into income flows #9558).
2. Replace taxable_social_security with the gross amount (social_security, or its components if SSI-style exclusions apply). Check the manual for any SSA-specific exclusions first.
3. Add tests to the existing SC TANF files (sc_tanf.yaml / integration.yaml):
   • a 2020 UC case (parent + child, $6,000 UC → $68.99/month);
   • a current-year case with SSA benefits below the taxation threshold, showing the benefit is now counted.
4. Fix both lines together. The SS change moves SC TANF in every year, so re-check the existing SC TANF expected values and microsim aggregates.

Context

Pre-existing issue P2 from Pavel's re-review of #9558 (2026-09-29). It was deferred from that PR because sc/tanf/income/unearned.yaml is outside its diff, a test would add an 8th changed test file (the selective-coverage cap), and the SS half is a behavior change unrelated to modeled UI.

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