Apply Colorado, Connecticut, Illinois and Indiana rules for a filer who can be claimed as a dependent

[MaxGhenis]

Summary

A return on which the filer, or on a joint return either spouse, can be claimed as a dependent on another return has no dependents (IRC 152(b)(1); Publication 501, Dependent Taxpayer Test), and a childless filer who can be claimed gets no EITC (IRC 32(c)(1)(A)(ii)(III)). Colorado, Connecticut, Illinois and Indiana build credits, exemptions and deductions on those rules, but their formulas never read claimed_as_dependent_on_another_return.

Stacked on the federal claimable-filer PR #10087 (claimable-filer-federal, head 35a2cbc, itself stacked on #10024); base this PR on claimable-filer-federal until both merge, and land it after #10051. The rules read the federal branch's inputs the way its own formulas do: "no dependents" (IRC 152(b)(1)) and the childless EITC bar read head_or_spouse_is_dependent_elsewhere_without_filing_exception, so the Publication 501 exception (the would-be claimant is not required to file and files at most for a refund) restores the dependents; rules that turn on an actual claim read claimed_as_dependent_on_another_return. A companion PR applies the same rules in DC, Georgia and Idaho: #10050.

Formula	Rule now	Source
co_eitc (ITIN and under-25 routes)	No childless credit when either filer can be claimed; a claimable filer with a qualifying child keeps it	C.R.S. 39-22-123.5(2.5) pays the credit the filer "would have been allowed, but for" a missing SSN; (2.7) pays the credit "allowed under section 32 (n)(1)" (HB23-1112, p.2-3). Neither waives the dependency bar.
co_ctc_qualifying_child (2022-2023), co_ctc_eligible_child (2024+)	No child on such a return	2022-2023: a share of the federal credit "a resident individual who claims a federal child tax credit" (HB23-1112, p.4). 2024+: the Department says the child "generally must meet the requirements for the federal child tax credit" (January 2026 guidance, p.2); see reading 1.
co_family_affordability_credit	No child on such a return	Same child test (January 2026 guidance); see reading 1
co_low_income_cdcc	Counts only children under 13 who are federal child care qualifying persons: none on such a return, except a child incapable of self-care	C.R.S. 39-22-119.5(3)(a)(III)-(IV): care for "a dependent of the taxpayer who is less than thirteen years old", and the individual "would be allowed a credit for the expenses under section 21" with enough liability. IRC 21(b)(1)(A) needs a dependent (none on such a return); 21(b)(1)(B) keeps a dependent incapable of self-care "without regard to subsections (b)(1)". See reading 6.
ct_property_tax_credit_eligible	Through 2021, the under-65 route needs a dependent the return can validly claim	C.G.S. 12-704c(b)(2): "for the taxable years commencing January 1, 2017, to January 1, 2021, inclusive", only a resident 65 or older or one "validly claiming one or more dependents"
ct_child_tax_rebate	No child on such a return	P.A. 22-118 sec. 411: a child claimed as a dependent on the 2021 federal return (TSSB 2022-5)
il_dependent_exemption	None on such a return	35 ILCS 5/204(c): one for each exemption "allowable ... under Section 151"
il_eitc (ITIN and age-18 extension)	No childless credit when either filer can be claimed	35 ILCS 5/212; 2025 Schedule IL-E/EITC instructions, p.5, question 6: "Can you be claimed as a dependent ... Yes. STOP"
il_ctc	Unchanged in behavior: a claimable filer keeps the credit for their own IRC 152 qualifying child (references and comment corrected to section 244)	35 ILCS 5/244(d): "qualifying child" has its IRC 152 meaning, which needs no allowable dependency; the 2026 draft instructions, p.2 say "at least one qualifying child"; see reading 2
il_income_tax_rebate_eligible, il_income_tax_rebate (2022 rebate on 2021 returns)	A filer actually claimed elsewhere is ineligible (reads the claim input, so a filer who can be claimed but is not keeps it); a joint return keeps $100 while one spouse is not claimed; no per-dependent amount on a return with a claimable filer	P.A. 102-0700 sec. 212.1(a), p.131-132: a taxpayer "who is claimed as a dependent on another individual's return for that year, is ineligible"; see reading 3
in_base_exemptions	Each filer keeps $1,000; dependents count only when no filer can be claimed	Information Bulletin 117, p.2: the own exemption stays "even if the individual can be claimed as a dependent"; 2025 IT-40 instructions, p.24 (state-authored copy; forms.in.gov blocks scripted downloads): "Could you, or your spouse if filing jointly, be claimed as a dependent on someone else's tax return? ... Yes. STOP. You cannot claim any dependents."
in_is_qualifying_dependent_child (additional and adoption exemptions)	No child on such a return	Same
in_nonpublic_school_deduction	None on such a return	Information Bulletin 107, p.1: a child who "qualifies as a dependent" under IRC 152

The contributed Illinois and Indiana dependent exemption reforms replace two of these formulas; at their default parameters they now match the baseline for a claimable filer (Indiana's reform also stops moving a barred child into its personal portion), with regression cases under both joint labellings.

Rows from the audit that need no change here:

• Already zero through the federal branch: Colorado's regular child care credit (co_cdcc reads the federal credit), Connecticut's and Indiana's EITCs (they match federal eitc, gated in Make rules for a filer claimed elsewhere independent of which spouse is labelled head #10024), and the federal student loan interest deduction that all four states start from. YAML cases here confirm the first three.
• Connecticut's post-2021 property credit: the audit flagged an obsolete age/dependent prerequisite from 2022, but age_threshold drops to 0 in 2022, so every filer qualifies, which matches 12-704c(b)(2)'s "2017, to January 1, 2021, inclusive". No bug.
• Illinois' personal exemption already applies its claimable-filer rule; its K-12 education credit uses custodian status, not dependency.

Not modeled (no new programs here): Colorado's property tax, rent and heat rebate (separate application, "Were you claimed as a dependent"), and Indiana's $200 fallback automatic refund (IC 4-10-22-4.5, actually claimed for 2022).

Readings for Max (queue via the US + core hub)

1. Colorado child tax credit (2024+) and family affordability credit. The statutes define the child only as a "qualifying child, as defined in section 152(c)" (HB23-1112, p.4; HB24-1311, p.3), which does not by itself require the child to be the filer's dependent. This PR follows the Department's January 2026 guidance that the child "generally must meet the requirements for the federal child tax credit", and its filing guide's dependents table ("your dependents will generally be the same as the dependents you claimed on IRS form 1040", Book 104, p.7). The same page says a custodial parent who cannot claim the child as a federal dependent and cannot claim the federal credit "cannot claim a Colorado Child Tax Credit for that child"; applying that to a claimable filer is an inference. Alternative (recommended by the second research lane): the statutory reading pays $1,200 (CTC) and $3,273 (2025 family credit) per young child to a claimable filer.
2. Illinois child tax credit. This PR follows 35 ILCS 5/244(d) and the 2026 draft instructions ("qualifying child"), so a claimable filer keeps the credit ($27.20 in the test household). The 2024-2025 instructions said "at least one child that is your dependent" (2025, p.1); reading that as a requirement gives $0 for 2024-2025. Section 244 itself has not changed since P.A. 103-592 (P.A. 104-417 only fixed a typo).
3. Illinois 2022 rebate, one claimed spouse. The exclusion is per taxpayer, so this PR keeps the $100 joint amount (no dependent amount). Alternatives: $50 (the qualifying spouse alone) or $0 (the joint return as one taxpayer, since "Spouses who qualify" are treated as a single taxpayer).
4. Childless EITC on a joint return (Colorado, Illinois). This PR bars the joint return when either spouse can be claimed, as Make rules for a filer claimed elsewhere independent of which spouse is labelled head #10024 does federally (Publication 596). Illinois' expanded worksheet skips its dependency question for joint filers; reading it literally would keep the credit.
5. Connecticut's 2022 child rebate reads claimability, not the claim input. Its "claimed" refers to the child being claimed on the taxpayer's 2021 return; whether a taxpayer can claim any dependent is IRC 152(b)(1), which turns on being claimable (with the Publication 501 exception), not on whether someone actually claimed the taxpayer. Alternative: read it as "the taxpayer was claimed" and use the claim input.
6. Colorado low-income child care credit for a disabled child. This PR keeps a child under 13 who is incapable of self-care, because 39-22-119.5(3)(a)(IV) imports the federal credit, which keeps such a dependent regardless of 152(b)(1) ($250 in the test household). Alternative: read Colorado's own "dependent of the taxpayer" ((2)(b): the meaning in IRC 152(a)(1)) as barred by 152(b)(1) too, giving $0.

Invariants

1. Swap invariance. Exchanging the two adults' head/spouse labels leaves every changed output unchanged, for any combination of claimed spouses.
2. Monotonicity. Marking another filer as claimed never raises a changed output (none of them is capped by a liability the claim can raise).
3. Identities. A return with a claimable filer has no Illinois dependent exemption, Colorado child tax credit, or Indiana additional exemption, and its Indiana base exemptions are $1,000 per filer.
4. Unchanged when nobody is claimed. Every changed formula reduces to its previous value when no filer can be claimed (checked by the microsimulation below).

Tests

• YAML: variable-named cases for every changed formula: a single claimable filer, a joint return with one claimable spouse under both head/spouse labellings, both spouses claimable, and nobody claimable, plus counterexamples (a claimable filer with a qualifying child keeps the Colorado EITC; a claimable filer aged 65 keeps the Connecticut credit; a two-return household). Expected values come from the statutes and repo parameters. RESULTS_PLACEHOLDER
• Property test policyengine_us/tests/core/test_claimable_filer_co_ct_il_in_invariants.py reuses check_swap/check_monotone from the federal invariants test in the four states for 2021, 2023, 2025 and 2026: Hypothesis batches check invariants 1 and 3; a seeded population checks 1-3. It covers tax-unit outputs (the person-level family affordability credit only through co_refundable_credits, for swaps), and its generator sets no nonpublic-school attendance, so that deduction is covered by YAML only. It caught a person/tax-unit broadcast in co_low_income_cdcc that one-return YAML cases cannot. PROPERTY_PLACEHOLDER

Microsimulation impact

MICROSIM_PLACEHOLDER

Follow-ups

• Colorado's family affordability credit is paused for 2026 and Idaho's child tax credit ended after 2025; both are fixed in Pause Colorado's family affordability credit in 2026 and leave Idaho's expired child tax credit out of 2026 totals #10051, which is not a dependency rule.

axiom: CO1 (EITC routes, child tax credit, family affordability credit, low-income child care), IL1 (dependent exemption, EITC, child tax credit) and IN1 (exemptions, nonpublic school deduction) queued as dispatch-ready drafts, not yet filed (d1247; the US hub files parity issues under d1142), in ~/reviews/us-hub/claimable-filer-rules/s1/axiom/out_co_ct_il_in.md with the 2026-10-11 addendum; CT 12-704c(b)(2) 2017-2021 gate n/a: expired and unencoded; CT P.A. 22-118 sec. 411 rebate n/a: expired and unencoded; IL sec. 212.1 rebate n/a: expired and unencoded; none encoded-correct

🤖 Generated with Claude Code

Merge with main after #10087

Merge commit 29a702c5f546338a6c350ec335aafee9d479d70a incorporates main after #10087 squash-merged as 2daebf2ca8, with main at 1ef55c1197c6b466912e2f081d548d277e04e360. Conflicts in nm_medical_expense_credit.py, nm_medical_expense_credit.yaml, and ca_cdcc_relevant_expenses.yaml take main's reviewed versions because this PR left all three unchanged from its federal base. Removed the obsolete federal changelog fragments claimable-filer-federal.fixed.md and head-dependent-elsewhere-swap.fixed.md. The exact replay check passes: the diff against main is byte-for-byte identical to git diff 35a2cbcbb9 3ebbde6840, preserving all 37 paths in this PR's original patch with no unrelated changes. No YAML syntax repair was needed.