Sec. 7. (a) If the amount determined under section 6(b) of this chapter for a taxpayer in a taxable year exceeds the taxpayer's state tax liability for that taxable year, the taxpayer may carry the excess over to the following taxable years. The amount of the credit carryover from a taxable year shall be reduced to the extent that the carryover is used by the taxpayer to obtain a credit under this chapter for any subsequent taxable year.
(b) A taxpayer is not entitled to a carryback or refund of any unused credit.