The subtraction is based on the age of the oldest spouse if you are filing Married Filing Jointly.
If not filing Jointly, for tax year 2025, there is a partial subtraction of up to 75% for those Michigan Taxpayers born after 1945 and before 1967.
Can this explain what you're seeing?
MLC Sec 206.30
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"