Dear Kenneth,
You are correct that SAM treats state tax credits (investment tax credit or production tax credit) as part of the project's federal taxable income. This seems consistent with the description in
IRS Publication 525
, under "Other Income, Recoveries," beginning on page 22 of the PDF document. SAM makes a simplification in assuming that the current year's state tax credit is taxable in the current federal tax year.
Best regards,
Paul.