Implement Delaware State Supplementary Payment (SSP)

[hua7450]

Summary

Implements Delaware's State Supplementary Payment (SSP) -- a federally-administered optional supplement for SSI recipients residing in certified adult residential care facilities, with frozen monthly amounts of $140 (individual) and $448 (couple).

Closes #7882

Regulatory Authority

• Delaware Code, Title 31, Section 505 (statutory basis)
• 16 Del. Admin. Code 13000-13640 (state administrative rules)
• SSA POMS SI PHI01415.008 (Delaware-specific administration, payment history 1992-2016)
• SSA POMS SI 01415.031-058 (annual federally-administered payment levels, 1999-2026)
• SSA State Assistance Programs for SSI Recipients, January 2011 (program overview, caseload)
• WorkWorld SSI State Supplement Delaware (eligibility summary, income/resource rules)

Program Overview

• Administration: Federally administered by SSA (for residential care supplement); DE DHSS/DSS administers a separate $5/month MAT supplement (not modeled)
• Funding: State funds
• Current caseload: 657 recipients (SSA State Assistance Programs, January 2011 -- last published edition)

Eligibility

Requirement	Source	How Modeled
Must be SSI-eligible (aged/blind/disabled)	SSA POMS SI PHI01415.008; SSA State Assistance 2011	is_ssi_eligible
Must be adult (age >= 18)	WorkWorld DE; SSA State Assistance 2011	age >= age_threshold parameter
Must reside in Delaware	State program (implicit)	defined_for = StateCode.DE
Must reside in certified adult residential care facility	SSA POMS SI PHI01415.008 (OS Code A)	de_ssp_living_arrangement enum (RESIDENTIAL_CARE)
No additional state income disregards	SSA State Assistance 2011; WorkWorld DE	Correct by omission -- uses federal ssi_countable_income
Federal SSI resource limits apply	SSA State Assistance 2011; WorkWorld DE	Delegated to is_ssi_eligible -> meets_ssi_resource_test
Non-facility residents receive $0	SSA POMS SI 01415.058 (OS Code Z)	Default enum value -> ineligible -> $0

Benefit Amounts (SSA POMS SI PHI01415.008; SI 01415.058)

Category	Monthly Amount	Source
Individual in certified residential care (OS Code A)	$140	POMS SI PHI01415.008; SI 01415.058 (FBR $994 + $140 = $1,134 for Jan 2026)
Couple in certified residential care (OS Code A)	$448	POMS SI PHI01415.008; SI 01415.058 (FBR $1,491 + $448 = $1,939 for Jan 2026)

Couple treatment: $448 is a combined total for the couple; divided by 2 for per-person attribution in PolicyEngine's person-level model. Uses both_eligible check — if only one spouse is SSP-eligible, they receive the individual rate ($140) per 42 USC §1382c(b)
COLA: Frozen since at least 1992 -- confirmed unchanged across all POMS annual tables from 1992 through January 2026

Payment calculation: State sets a total payment standard (FBR + supplement). Federal SSI and countable income are deducted. Remainder is the state supplement. Implemented using the uncapped_ssi reduction pattern: max(0, supplement - max(0, -uncapped_ssi)).

Not Modeled (by design)

What	Source	Why Excluded
MAT program ($5/month state-administered supplement)	SSA POMS SI PHI01415.008; WorkWorld DE	Narrow population (5 recipients in 2011), requires tracking SSI-to-SSDI transition, de minimis amount
OS Code Y (waived supplementation)	SSA POMS SI 01415.058	Voluntary waiver -- not simulatable
Mandatory minimum (pre-1974 grandfathered recipients)	SSA State Assistance 2011; DE Admin Code 13433	Grandfathered population only, dwindling to near zero
Certification form requirement	SSA POMS SI PHI01415.008	Administrative/procedural, not simulatable
Interim assistance reimbursement	SSA State Assistance 2011	Administrative arrangement between state and SSA
Passalong method (maintaining payment levels)	SSA State Assistance 2011	Automatic for frozen amounts -- nothing to model
Financial responsibility of relatives	SSA State Assistance 2011	None exists for DE
Recoveries, liens, and assignments	SSA State Assistance 2011	None exists for DE

Files

policyengine_us/parameters/gov/states/de/dhss/ssp/
  age_threshold.yaml
  amount/
    individual.yaml          # $140/month from 1992-01-01
    couple.yaml              # $448/month from 1992-01-01

policyengine_us/variables/gov/states/de/dhss/ssp/
  de_ssp_living_arrangement.py   # Enum input: RESIDENTIAL_CARE / NONE
  de_ssp_eligible.py             # Eligibility: SSI-eligible + age 18+ + residential care
  de_ssp.py                      # Benefit calculation with uncapped_ssi reduction

policyengine_us/tests/policy/baseline/gov/states/de/dhss/ssp/
  de_ssp_eligible.yaml           # 6 eligibility tests
  de_ssp.yaml                    # 8 benefit amount tests (incl. asymmetric couple)
  integration.yaml               # 7 integration tests

Verification TODO

• Verify payment amounts against SSA POMS SI 01415.058 and SI PHI01415.008
• Verify eligibility logic against SSA POMS SI PHI01415.008 and WorkWorld DE
• Verify amounts current as of 1992-2026 (all POMS annual tables confirm $140/$448 frozen)
• CI passes

Test plan

• 21 tests pass (6 eligibility + 8 benefit + 7 integration)
• CI passes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (941b142) to head (940a332).
⚠️ Report is 127 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##             main     #7883       +/-   ##
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+ Coverage   71.46%   100.00%   +28.53%     
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  Files        4099         3     -4096     
  Lines       59132        49    -59083     
  Branches      288         0      -288     
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- Hits        42257        49    -42208     
+ Misses      16869         0    -16869     
+ Partials        6         0        -6     

Flag	Coverage Δ
unittests	100.00% <100.00%> (+28.53%)	⬆️

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