The TT12 and TAX are file formats used to store tax return data for application called TurboTax. You are able to view content of these files in the TurboTax for Windows, or Mac, but there is no reason to convert them, because it is the same file format, only with different file extension.
Convert TurboTax 2012 tax return file to TurboTax tax return file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert tt12 to tax on Windows
A tax preparation software developed by Intuit
Convert from tt12 file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.