Sorry---you cannot purchase software farther back than 2019 from TurboTax because it is no longer supported and cannot be updated. You might find it on eBay etc but you will not be able to use it to get accurate results since it cannot be updated. And....it is too late to receive a refund for a tax year earlier than 2019. Earlier refunds have now been forfeited. If you owe tax due, you will still have to pay with interest and penalties.
You might want to seek paid local tax help if you are behind for that many years.
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?
Or....use the paper forms and prepare them by hand to mail in. Each year must be mailed in its own envelope. Do not try to combine them in any way.
2015
Form 1040 https://www.irs.gov/pub/irs-prior/f1040--2015.pdf
Form1040 Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2015.pdf
Form1040A https://www.irs.gov/pub/irs-prior/f1040a--2015.pdf
Form 1040A Instructions https://www.irs.gov/pub/irs-prior/i1040a--2015.pdf
Form 1040EZ https://www.irs.gov/pub/irs-prior/f1040ez--2015.pdf
Form 1040EZ Instructions https://www.irs.gov/pub/irs-prior/i1040ez--2015.pdf
2016
Form 1040 https://www.irs.gov/pub/irs-prior/f1040--2016.pdf
Form 1040 Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2016.pdf
Form 1040A https://www.irs.gov/pub/irs-pdf/f1040a.pdf
Form 1040AInstructions https://www.irs.gov/pub/irs-prior/i1040a--2016.pdf
Form1040EZ https://www.irs.gov/pub/irs-prior/f1040ez--2015.pdf
Form1040EZ Instructions https://www.irs.gov/pub/irs-pdf/i1040ez.pdf
Remember to prepare your state return as well—if you live in a state that has a state income tax.
2017
https://www.irs.gov/pub/irs-prior/i1040gi--2017.pdf
https://www.irs.gov/pub/irs-prior/f1040--2017.pdf
https://www.irs.gov/pub/irs-prior/f1040a--2017.pdf
https://www.irs.gov/pub/irs-prior/i1040a--2017.pdf
https://www.irs.gov/pub/irs-prior/f1040ez--2017.pdf
https://www.irs.gov/pub/irs-prior/i1040ez--2017.pdf
nowhere really. Turbotax no longer supports those years. you can find offers for them on the web but they can not be updated and no state returns are available. if you open your .tax#### with them you could easily change the return from what was filed.
However, there is a website we do not vouch for that you can e-mail the .tax#### files to and for a fee you'll get a print out
you can file form 4506-T with the IRS to get transcripts - free
or 4506 to get copies $43/per year- time may be running out for 2015
https://www.irs.gov/pub/irs-pdf/f4506.pdf
https://www.irs.gov/pub/irs-pdf/f4506t.pdf