I had been out of the country from 2014-Nov 2017 and have not filed US taxes since 2014. Can I claim all of the interest for Student loans from 2015 to current?
A 2015 1098-E can only be reported on a 2015 tax return for a refund. The 3 years statute of limitation to file for a 2015 refund will expire on April 15, 2019, so you only have 8 days to file for a 2015 refund.
You can purchase 2015 software here:
https://turbotax.intuit.com/personal-taxes/past-years-products/
To file a return for a prior tax year
If you need to prepare a return for 2015, 2016, or 2017 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 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.
As has already been mentioned, a 2015 return must be filed no later than April 15, 2019, or any refund will be forfeited.