Can I find out what year I last filed my taxes?

And.....have you been receiving taxable income since the last time you filed a tax return?  Why are you asking now about when you last filed?     Have you fallen behind on filing, and are you now trying to figure out where to start in order to get caught up?

What if I do not file my tax return?

https://ttlc.intuit.com/questions/2572308-what-happens-if-i-don-t-file-my-taxes

Who has to file?

http://www.irs.gov/uac/Do-I-Need-to-File-a-Tax-Return%3F

TurboTax has software for 2021 onward.   Software is no longer available from TurboTax for earlier years, nor would it be supported even if you find it on eBay, etc.  Updates are not available.   It is also too late to receive a tax refund for a tax year earlier than 2021---those refunds have been forfeited.   BUT if you owe tax due you still have to pay with penalties and interest.   There might be other software providers that have software for those years, but you will not receive refunds for the returns even if the forms show a refund.

It might be better for you to seek local paid tax help in a situation when you are several years behind in filing your tax returns.  Do you even have all of the documents you will need to enter and show your income—like your W-2’s and any 1099’s?

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/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/00/25573 

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/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.

Refunds for tax years 2020 or earlier have been forfeited and will not be paid to you even if shown on the tax return form.  But if you owe tax due, you will still have to pay, and you will be billed later for the interest and penalties owed.  TurboTax will not calculate the penalties or  interest.   That will be done by the IRS/state after they receive your return with your payment of the tax due as shown on the tax form(s).