You may be able to subtract some or all of your taxable federal pension included in your federal income. This includes benefits paid to the retiree or the beneficiary. The subtraction amount is based on the number of months of federal service before and after October 1, 1991:
To determine your percentage, divide your months of service or points earned before October 1, 1991, by your total months of service or points earned. Round your percentage to three places (example: 0.4576 = 45.8%). Once you determine the percentage, it will remain the same from year to year.
For more information, see Form 40 Instructions.