Going forward...make sure you print out a copy for yourself every year.
IF you download as a PDF file, you can also save that to USB flash drive, and keep in a safe place. (Computers crash/replaced etc.....so keep a copy of the PDF on a USB every year)
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1) If you've used the TTX "Online" software every year, you can get/download/save the past 7 yrs of PDF files now.
2) If you've used the TTX "desktop" software every year, you those files are only on that computer, so keep backup copies of the PDF file. (the tax datafiles can only be read by the software, and only the last 3 years can be loaded and used..so the PPDFs are critical)