Trying to catch up on filing taxes for 2016-2018. Have turbotax deluxe for 2016 but need 2015s (filed through turbotax) records to continue, how do I get those?

[xmasbaby0]

Edited--I see you say you filed a 2015 return using TurboTax.  But you did not say if you used online TT or desktop software.

Many people have multiple TT accounts and forget how to access them.  Log out of the account you are in now.

Account recovery

https://myturbotax.intuit.com/account-recovery/

https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-online-user-id-or-password

Or did you use the desktop version of TurboTax?  If so, the files are on your own hard drive or any backup device you used like a flash drive.

https://ttlc.intuit.com/questions/1901486-how-many-turbotax-accounts-do-i-have

https://ttlc.intuit.com/questions/1901535

https://ttlc.intuit.com/questions/1901659-find-your-tax-data-file-in-mac

https://ttlc.intuit.com/questions/1900721-find-your-tax-data-file-tax-file-in-windows

How to transfer last year’s return? https://ttlc.intuit.com/questions/1900883

As for 2016 through 2018:

To file a return for a prior tax year

If you need to prepare a return for 2016, 2017, or 2018 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/

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.

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.

[xmasbaby0]

Mail each year's tax return in its own separate envelope--do not put them together to save postage or you risk having one overlooked or thrown away.  And mail federal and state returns separately to the correct addresses for federal and state.