Sorry--TurboTax accounts cannot be merged. Pick one and stick with it going forward. Keep a record for yourself of how to access the one you will not use so that you can get into it if you need to.
Always save a PDF of the return AND the .taxfile for your records so you always have access to them ...
Save a Backup Copy of Your Tax File
To save a backup copy of your tax data file (.tax file) that can be opened and read by TurboTax CD/Download software, you'll need to choose your TurboTax product:
Similar-sounding—but very different—is saving a copy of your tax return as a PDF file, which is like a picture or "snapshot" of your tax return that you can view or print.
PDF files cannot be opened or read by TurboTax software, which means they cannot be used for amending or troubleshooting calculation issues.