Sounds like you're trying to figure out the non-Massachusetts portion of deductions. It may not be as straightforward as looking at your W-2.
The "non-MA" portion is the part of your deductions that are attributed to non-MA income.
If
you were a non-resident, it's easier to figure the MA portion first,
then subtract it from the total deductions to get the non-MA portion.
To calculate the MA portion: Divide your MA-source income (subject to taxation by MA) by the total of all income that
would be taxable by MA
if you were a full-year resident. Multiply the resulting fraction by your total deductions.
If you were a part-year resident, divide the number of days you lived outside of MA by 365. Multiply the resulting fraction by your total deductions, to get the non-MA portion.
