Ye writes, "After submitting my application for naturalization, I realized that in one of the tax years, we had mistakenly declared ourselves as non-residents, though, we were technically part-year residents (since we moved to the state in the middle of the year). I have now corrected my return and my state has accepted it. What should I do? Should I tell the USCIS about it right away or wait till I go for the interview? Will it mess up my application?"
It is best that you either wait for a letter (in form of a request for evidence or RFE, something that USCIS does when it finds something is not right or there is a discrepancy) in the mail, and if you do not get it, then, you wait for the interview. During the interview, you will be asked if there is any change in your application, and at that point you can present the corrected tax form and explain the error. As far as USCIS is concerned, what they care about is that you do not owe anything to the IRS or to the state before approval. So as long as you have documents that clearly demonstrate that you have paid all your taxes, you are good.