In general
The credit allowed under subsection (a) for any taxable year shall not exceed the excess (if any) of the taxpayer’s net income tax over the greater of—
(A)#
the tentative minimum tax for the taxable year, or
(B)#
25 percent of so much of the taxpayer’s net regular tax liability as exceeds $25,000.
For purposes of the preceding sentence, the term “net income tax” means the sum of the regular tax liability and the tax imposed by section 55, reduced by the credits allowable under subparts A and B of this part, and the term “net regular tax liability” means the regular tax liability reduced by the sum of the credits allowable under subparts A and B of this part.