What is the add back to prevent a double benefit on the donation and how does it work?

LA R.S. 47:6301(A)(1)(a) provides that a “taxpayer shall not receive any other state tax credit, exemption, exclusion, deduction or any other tax benefit for when the taxpayer has received” the credit for donations to school tuition organizations. For Louisiana income tax purposes, the starting point for corporation and fiduciary income tax returns is federal taxable income and the starting point for individual income tax is federal adjusted gross income. The prohibition on double benefits requires that a taxpayer add back certain deductions taken at the federal level that are otherwise deductible for state income tax purposes. If a taxpayer does not take the corresponding deduction related to the donation, no add back is required.