Maine EITC omits the §5219-S expansion: childless filers age 18-24 get $0 instead of 50% of a pro forma federal EIC

[DTrim99]

Bug

me_eitc is computed as the actual federal EITC times the Maine match rate:

def formula(tax_unit, period, parameters):
    federal_eitc = tax_unit("eitc", period)
    ...
    return federal_eitc * match_rate

But Maine decouples from the federal childless age test. 36 M.R.S. §5219-S:

• sub-§6 (TY2020+): "eligible individual" also includes "an individual who does not have a qualifying child for the taxable year, who is at least 18 years of age and has not attained 25 years of age before the close of the taxable year";
• sub-§5: for such individuals the credit "must be calculated in the same manner as it would be calculated if that individual were eligible for a federal earned income credit";
• sub-§7 (TY2021+): ITIN filers likewise qualify notwithstanding IRC §32(m).

The 2025 ME EIC worksheet implements this via a pro forma federal Worksheet A with the Step 4 age question answered as if the age floor were 18.

Reproduction

2025, ME, MFJ, ages 23/24, no dependents, $10,476 wages (from PolicyEngine/policyengine-taxsim#1056; TaxAct return attached there):

• PolicyEngine: eitc = 0 (correct federally — both spouses under 25), me_eitc = 0
• Expected: pro forma childless federal EIC = $649 (2025 max; earned income above the $8,490 phase-in end, AGI below the $17,730 MFJ phase-out start), × 50% = $324.50. TaxAct shows $325 on Form 1040ME.

Aging the same couple to 25/26 in PolicyEngine yields eitc = 649 and me_eitc = 324.50, confirming only the age gate blocks the credit.

Fix sketch

New Jersey models the same expansion (nj_childless_eitc_age_eligible, used in nj_eitc), though it approximates the pro forma credit with the childless maximum. Since eitc_phased_in and eitc_reduction are age-independent, Maine can compute the pro forma amount exactly: for childless tax units that fail only the federal age test and have a head or spouse aged 18–24, use max(0, eitc_phased_in - eitc_reduction). The ITIN half of the expansion (sub-§7) is likely out of scope since PolicyEngine does not model ITIN status.

Found while diagnosing PolicyEngine/policyengine-taxsim#1056. cc @PavelMakarchuk