Your tax due will be on the 1040 line 37. When did you mail it? Did you use the Online version LAST year and just print it out now to mail or did you use the Desktop installed program? If you used Online then print out a copy for yourself (which you should do anyway). Yes the 2023 tax due payment was due April 15, 2024 so the IRS might send you a bill for a penalty and interest.
How to Access prior year online returns
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/270...
If you can't get the side menus to open up to access the prior year..... You need to start entering some basic Personal Info in 2024 for the side menu to open up. Just continue a little ways into 2024. I had to go though about 12 screens.
