In general

For purposes of this section, the term “regular tax” means the regular tax liability for the taxable year (as defined in section 26(b)) reduced by the foreign tax credit allowable under section 27(a). 1 1 See References in Text note below. Such term shall not include any increase in tax under section 45(e)(11)(C), 49(b) or 50(a) or subsection (j) or (k) of section 42.