State tax filing

In the MA program, you must enter the contributions previously taxed by Mass. If you cannot prove the amount, it is zero. If you have old tax returns or financial documents, you may be able to determine the amount taxed. 

The state of MA has very different laws than the federal regarding IRAs and is much more complicated. The Jan 2023 update of MA treatment of Roth states: Further, Massachusetts allows a deduction for the portion of IRA distributions that were previously subject to Massachusetts personal income tax. The distributions are deducted from Massachusetts gross income to the extent that the aggregate amount deducted equals the aggregate amount previously included in Massachusetts gross income. 

This means you must be able to show what has been taxed and the remainder is taxable. Income to the decedent is income to you.  Enter the amount you know has been taxed and can prove, in case of audit. Best case would be if you could determine all contributions and distributions to enter here.