Sorry, Online is only for 2024 now. Online for 2023 and prior is closed now so you can not start a new 2023 or prior return or finish one. You have to do each year separately
Then when you do file 2024 enter 0 for the 2023 AGI since you are filing 2023 late.
You have to print and mail prior year returns. When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return. Don’t forget state.
If you do not owe or will get a refund for 2023, there is no penalty for filing late. If you owe tax due, your late filing penalties and interest have been adding up since last year's filing deadline, so get it mailed asap with your payment of the tax due as shown on the tax return and then expect a bill for the additional amount you will owe. You have also missed the chance to request an extension for 2024, so the same advice applies.
You can only file 2023 by mail. 2024 can be e-filed, but you will need to use "zero" as your AGI when you try to e-file 2024, since the IRS will not have a 2023 AGI in the system for you.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**