Originating issue: PolicyEngine/policyengine-taxsim#1078 ("exepy.txt shows 5000 in unidentified credits and 4020 in rebate"). Not addressed by #8970.
Summary. mt_non_refundable_credits is a Person-entity variable with adds = gov.states.mt.tax.income.credits.non_refundable; the 2021 list includes mt_income_tax_rebate, a TaxUnit-entity variable ($2,500 joint). The tax-unit value is projected onto every member, so a joint couple receives 2 × $2,500 = $5,000 of credit — wiping liabilities up to $5,000 instead of $2,500. Per MCA 15-30-2191(1) (2023 MCA, temporary; enacted by HB192, Laws 2023), the rebate is "the lesser of: (a) the qualified taxpayer's 2021 individual income tax liability as properly reported on line 20 of the 2021 Montana individual income tax return; or (b) ... (ii) for a married couple filing a joint return, $2,500" — and 15-30-2191(2) separately bars issuing any rebate "that exceeds the taxpayer's individual income tax liability as properly reported on line 20".
On the taxsim #1078 record this zeroes a $4,020 (PE-basis) pre-credit liability, and even flips the mt_files_separately election (the doubled credit zeroes the joint path first), so the election comparison itself is distorted.
PR #8970 does not fix this: it caps the variable's own value and scopes the amounts to 2021, but leaves the per-person projection — with #8970 applied, this record still nets 2 × $2,500 = $5,000. Filing separately so the two can land independently.
Suggested fix: apply the rebate once per return (unit-level credit application; or a person-level rebate of $1,250 per head/spouse capped at own-column liability for the separate-on-same-form path).
Integration test: the #1078 couple (see #9011) → total MT non-refundable credits attributable to the rebate = $2,500 (currently $5,000); with the SS-threshold issue also fixed, 2021 mt_income_tax net of rebate ≈ 3,310 (TaxAct tax before credits 5,810 − 2,500).
Originating issue: PolicyEngine/policyengine-taxsim#1078 ("exepy.txt shows 5000 in unidentified credits and 4020 in rebate"). Not addressed by #8970.
Summary.
mt_non_refundable_creditsis a Person-entity variable withadds = gov.states.mt.tax.income.credits.non_refundable; the 2021 list includesmt_income_tax_rebate, a TaxUnit-entity variable ($2,500 joint). The tax-unit value is projected onto every member, so a joint couple receives 2 × $2,500 = $5,000 of credit — wiping liabilities up to $5,000 instead of $2,500. Per MCA 15-30-2191(1) (2023 MCA, temporary; enacted by HB192, Laws 2023), the rebate is "the lesser of: (a) the qualified taxpayer's 2021 individual income tax liability as properly reported on line 20 of the 2021 Montana individual income tax return; or (b) ... (ii) for a married couple filing a joint return, $2,500" — and 15-30-2191(2) separately bars issuing any rebate "that exceeds the taxpayer's individual income tax liability as properly reported on line 20".On the taxsim #1078 record this zeroes a $4,020 (PE-basis) pre-credit liability, and even flips the
mt_files_separatelyelection (the doubled credit zeroes the joint path first), so the election comparison itself is distorted.PR #8970 does not fix this: it caps the variable's own value and scopes the amounts to 2021, but leaves the per-person projection — with #8970 applied, this record still nets 2 × $2,500 = $5,000. Filing separately so the two can land independently.
Suggested fix: apply the rebate once per return (unit-level credit application; or a person-level rebate of $1,250 per head/spouse capped at own-column liability for the separate-on-same-form path).
Integration test: the #1078 couple (see #9011) → total MT non-refundable credits attributable to the rebate = $2,500 (currently $5,000); with the SS-threshold issue also fixed, 2021
mt_income_taxnet of rebate ≈ 3,310 (TaxAct tax before credits 5,810 − 2,500).