Can I file taxes from 2015 to now on turbo tax?

No.   Software is no longer available for 2015 or 2016.   The online program is only for 2020 returns--no other year.   And it is too late to get a refund for a 2015 or 2016  return, but if you owe tax due you still have to pay.   You can use the paper forms and prepare them by hand to mail in.

https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment

PRIOR YEAR FORMS FROM IRS

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/i1040gi--2016.pdf

 Form 1040EZ Instructions  https://www.irs.gov/pub/irs-pdf/i1040ez.pdf

The current online program can only be used for a 2020 return--no other year.  And if you did not file a 2019 return you will have trouble e-filing 2020.  When it asks for your 2019 AGI try using zero.  If zero does not work then you have to print, sign and mail 2020.

Online preparation and e-filing for 2017, 2018 and 2019 is permanently closed.

To file a return for a prior tax year

 If you need to prepare a return for 2017, 2018, or 2019 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.

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.

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.

If you are getting a refund, there is not a penalty for filing past the deadline.  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.

Note:   A 2017 refund will be forfeited unless the 2017 return is filed by May 17, 2021.

If you live in a state with a state income tax, remember to prepare a state return.   Get the 2015 form from the state's tax site.

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.