In general. A tax meets the requirements of section 6362(b) and this section only if it is imposed on the amount of the taxable income, as defined in section 63, of the individual, estate, or trust, adjusted—

By subtracting an amount equal to the amount of the taxpayer's interest on obligations of the United States which was included in his gross income for the taxable year;

By adding an amount equal to the amount of the taxpayer's net State income tax deduction, as defined in paragraph (a) of § 301.6362-4, for the taxable year;

By adding an amount equal to the amount of the taxpayer's net tax-exempt income, as defined in paragraph (b) of § 301.6362-4, for the taxable year; and

If a credit is allowed against the tax in accordance with paragraph (b)(3) of this section for sales tax imposed by the State or a political subdivision thereof, by adding an amount equal to the amount of the taxpayer's deduction under section 164(a)(4) for such sales tax.

Permitted adjustments. A tax which otherwise meets the requirements of paragraph (a) of this section shall not be deemed to fail to meet such requirements solely because it provides for one or more of the following adjustments:

A credit meeting the requirements of paragraph (c) of § 301.6362-4 is allowed against the tax for the taxpayer's income tax liability to another State or a political subdivision thereof.

A tax is imposed on the amount taxed under section 56 (relating to the minimum tax for tax preferences).

A credit is allowed against the tax for all or a portion of any general sales tax imposed by the State or a political subdivision thereof with respect to sales either to the taxpayer or to one or more of his dependents.

Method of making mandatory adjustments. The mandatory adjustments provided in paragraph (a) of this section shall be made directly to taxable income. Except as provided in paragraph (c)(2) of § 301.6362-4, no account shall be taken of any reduction or increase in the Federal adjusted gross income which would result from the exclusion from, or inclusion in, gross income of the items which are the subject of the adjustments. Thus, for example, when for purposes of the calculation the taxpayer's Federal taxable income is adjusted to reflect the exclusion from gross income of interest on obligations of the United States, no change shall be made in the amount of the taxpayer's deduction for medical expenses, or in the amount of his charitable contribution base, even though such amounts would ordinarily depend upon the amount of adjusted gross income.