Well look on the PC for any other .tax2018 files. Maybe you have another one. Search the whole computer for all files ending in .tax or .tax2018. Check the recycle bin and For Windows 10 check the One Drive. Did you make any backups? Like DropBox.
Also there should be a ,tax file starting with a Tilde ~ sign in case your real file get corrupted. I would rename it and take off the ~ sign or it might not open on Mac.
