When you have only W-2s, the easiest and cheapest way to prepare and file tax returns for each year is to download the blank forms from the IRS and fill time out and mail them in with a copy of the W-2. You should mail each year in a separate mailing envelope. Here is where to find them to download: https://www.irs.gov/forms-pubs/prior-year
You could buy and download a program and install it on your computer for each year for 2016, 2017 and 2018 using TurboTax. See here: https://turbotax.intuit.com/personal-taxes/past-years-products/
All of these returns must be printed and mailed. They can't be efiled. You can still get a refund from all 3 of these years but the 2016 return must be filed by July 15 to get a refund.
TurboTax no longer has software available for 2013, 2014, and 2015. It is too late to file those years for a refund. You are required to file them however, if you owe taxes.
