Per Indiana IT-40 Booklet on page 12:

Line 1 – Tax Add-Back

If you did not complete Federal Schedules C, C-EZ, E, or F, which include sole proprietorship income, farm income, rental, partnership, S corporation, and trust and estate income (or loss), then do not complete this line.

On those schedules you are allowed to claim a deduction for taxes paid which are:

• based on, or
• measured by income, and
• levied at a state level by any state in the United States.

If you claimed this kind of deduction on any of these schedules, then you must add it back to your Indiana income. Do not add back property taxes on this line.

Note. Income, losses and/or expenses from other schedules and forms may flow through to federal Schedules C, E and F. For example, partnership income from federal Schedule K-1 (Form 1065) may be included on federal Schedule E, while expenses from federal Form 8829 may be included on federal Schedule C. Make sure to check these schedules and forms for any deduction that needs to be added back.

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.