If you placed an asset in service before tax year 2020 and you claimed the bonus depreciation allowance or section 179 expensing for qualified property on your federal return, complete schedule M1M, Income Additions and Subtractions.
You will need to add back 80% of the section 179 deduction in the year that the full deduction is claimed on the Federal tax return. In the subsequent years after the addition is claimed, you may complete the Line 21 Worksheet from the M1M instructions to determine your subtraction amount for each year.
This addition is not required for assets placed in service after December 31, 2019. You can review this information here.
Minnesota M1M Instructions - page 11 for Other Additions; page 13 for Other Subtractions