Sorry, you can only file 2019 online now. To do prior years you have to buy the Desktop program. They only sells the last 3 years so 2016-2018. You have to buy a separate program for each year. You need a full Windows or Mac computer to install it on. Buy the download here
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.
Important! Mail Federal and State in separate envelopes and mail each year in separate envelopes.
If you are getting a refund, there is not a penalty for filing past the deadline. You have 3 years to file for a refund. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.
How to file a prior year
Or If you have a simple return You can fill out the blank forms for free. Here are some for 2018. You can find other years at https://apps.irs.gov/app/picklist/list/priorFormPublication.html
Here is the IRS 2018 Form 1040
And 2018 Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf
2018 Tax and EIC Tables https://www.irs.gov/pub/irs-prior/i1040tt--2018.pdf
IRS 2018 Schedules 1 thru 6 (only if needed)
Sch 1 : https://www.irs.gov/pub/irs-prior/f1040s1--2018.pdf
Sch 2 : https://www.irs.gov/pub/irs-prior/f1040s2--2018.pdf
Sch 3 : https://www.irs.gov/pub/irs-prior/f1040s3--2018.pdf
Sch 4 : https://www.irs.gov/pub/irs-prior/f1040s4--2018.pdf
Sch 5 : https://www.irs.gov/pub/irs-prior/f1040s5--2018.pdf
Sch 6 : https://www.irs.gov/pub/irs-prior/f1040s6--2018.pdf
Since TurboTax does not have programs available for any of the earlier years, you will have to go to a paid tax preparer to get them prepared unless you want to do it by hand using the IRS forms. You cannot get a refund for any years earlier than 3 years from the original filing date. However, if you owe taxes on any of those returns, you must pay them.