T11 and T12 are file formats used to store tax return data from application called At Home. You can view content of these files in the program itself, but a conversion does not make much sense to be honest. These files contains data from two separate years so not something you would usually convert, but maybe it is somehow doable in the program.
Convert At Home 2011 tax return file to H&R Block At Home 2012 tax return file.
We found 2 software records in the database related to .t11 to .t12 file format conversion.
Microsoft Windows software - convert t11 to t12 on Windows
A popular tax preparation software from HRB Digital
Convert from t11 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned t11 to t12. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert t11 to t12 on OS X
A complete a simple federal tax return software