federal is due by midnight on 7/15/2020. if it's submitted on or before that date you get a few extra days to correct and refile. you didn't mention which state. some did not extend their usual due date so now it could be late.
I get it that I'm late, both for the federal and state returns. (West Virginia). My question is how can I file? Does the turbotax allow for later filing, or do I have to file by regular mail?
E-filing remains open until October 15, 2020.
If you are getting a refund, there is not a penalty for filing past the deadline. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.