There is only one file type that uses the .TAX2017 extension:
TurboTax 2017 Tax Return
A TAX2017 file is a United States tax return created with the 2017 version of Intuit TurboTax. It contains information about a user's tax return, which includes personal information, federal IRS tax forms, and one or more state forms for the 2017 tax year. TAX2017 files may be encrypted if saved with password protection since they store sensitive personal and financial data.
Updated: February 26, 2019