I didn't file a return for 2023 and I was supposed to. What can I do to file for 2023, being that it's now 2025...?

Sorry it's too,late to start a 2023 or prior online return or use the mobile app, either on Turbo Tax or the IRS.  And too late to efile 2023.

If you need to do 2023 or prior you can buy the Desktop download here,

TurboTax 2022 Prior Year Tax Prep - File Past Years' Taxes

You will need a full Windows or Mac to install it on.

If you have a simple return and want to file for free you can fill out the forms by hand.  Here are some basic forms.....

Here is the 2023 1040 return

https://www.irs.gov/pub/irs-prior/f1040--2023.pdf

or if you want bigger type use 1040SR for Seniors,

https://www.irs.gov/pub/irs-prior/f1040s--2023.pdf

2023 1040 Instructions

https://www.irs.gov/pub/irs-prior/i1040gi--2023.pdf

2023 EIC and Tax Tables

https://www.irs.gov/pub/irs-prior/i1040tt--2023.pdf

Schedules 1-3

https://www.irs.gov/pub/irs-prior/f1040s1--2023.pdf

https://www.irs.gov/pub/irs-prior/f1040s2--2023.pdf

https://www.irs.gov/pub/irs-prior/f1040s3--2023.pdf

Don’t forget your state.  And you will have to print and mail your returns.  So be sure to attach copies of your W2s and any 1099s that have withholding on them.  You have to mail federal and state in separate envelopes because they go to different places.  Get a tracking number from the post office when you mail them for proof of filing.

Then when you file for 2024 you need to enter 0 for the 2023 AGI since you are filing 2023 late.

You cannot change the tax year.   The current online program is for 2024 only.   Only a 2024 return can be prepared online and only a 2024 return can be e-filed.

Online preparation and e-filing for 2021, 2022, and  2023 is permanently closed.

Note:  The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac.  It cannot be used on a mobile device.

To file a return for a prior tax year

 If you need to prepare a return for 2021, 2022, or 2023  you can purchase and download desktop software to do it, then print, sign,  and mail the return(s)

https://turbotax.intuit.com/personal-taxes/past-years-products/

You may also want to explore purchasing the software from various retailers such as Amazon, Costco, Best Buy, Walmart, Sam’s, etc.

Remember to prepare your state return as well—if you live in a state that has a state income tax.

https://ttlc.intuit.com/turbotax-support/en-us/help-article/state-taxes/contact-state-department-revenue/L9qVToi02_US_en_US?uid=m6e06um0

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 certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.