Charitable contribution deductions from Adjusted Gross Income (AGI) are $300 for 2020 (single/joint) or the $300 (single) and $600 (joint) for 2021. Are these deductions from AGI in 2020 and 2021 added back to reach Michigan taxable income?

No. If a charitable cash contribution is deducted to reach federal (AGI) it is not added back to reach Michigan taxable income.