How do I pay state taxes on my IRA gains?

Q: My wife and I have contributed to our IRAs on and off for the last 20 years and we realize we have to pay fed taxes on everything as we withdraw. But we didn't realize we have to pay state taxes on all of our gains (but not our contributions). What to we do if we cannot determine what part of our balance is contributions and what is gains? - Jack, Weymouth

The following answer was provided by Wesley Rickard CPA, Quin, Rickard, Lipshires, & Grupp LLP, Norwood.

A: If you are unable to accurately determine you original contributions which can be withdrawn tax free for state purposes than take the best guess you can based on how many years you think you contributed.