If this is related to Form M1PR - You may file and claim a refund for up to one year after the original due date of August 15th. If you file later, you won’t receive a refund.
You can't file a previous year M1PR return through TurboTax. Instead, file directly through the Minnesota Department of Revenue.
For 2015: http://www.revenue.state.mn.us/Forms_and_Instructions/m1pr_15_fillin.pdf
@dstarlight2003 You added on to someone else's thread, so we do not know if you are asking about MN.
If you are asking about MN you can go back one year from the filing due date: