My husband doesn’t qualify for public pension deduction on form M1M line 29.

To revisit that section:

1. Open MN return 
2. Continue to the Screen Tell Us About Other Income Adjustments
3. Scroll down to Received Pension from Qualified Public Pension Plans.

To qualify, all of these must be true: 

• You receive payments or survivor benefits from a qualified pension plan. 
• Your payments are taxable on your federal return.
• You meet a certain income limit based on your filing status. 
• Your payments are not based on service for which you also earned credit toward Social Security benefits.
  • If you are eligible to receive Social Security benefits based on your service, your payments will not qualify. Your benefits may be eligible for the Social Security Benefit Subtraction.
• If you earned credit toward Social Security benefits for only a portion of your service.

For more information check here.