(a) If a taxable entity is eligible for a credit that exceeds the limitations under § 171.556, the taxable entity may carry the unused credit back for not more than three tax years or forward for not more than 10 consecutive reports following the tax year in which the allocation certificate was issued. A credit carryforward from a previous report is considered to be used before the current year installment. A credit carried back to a previous report is considered to be used after any other franchise tax credit is applied to that report.
(b) A credit that is not used may not be refunded.

(c) The allocation of a credit in accordance with § 171.559 does not extend the period for which a credit may be carried forward and does not increase the total amount of the credit that may be claimed.
(d) An entity may not carry back a credit under this subchapter to a tax year for which the report was originally due before January 1, 2026.