Is the IRS on his case for those old years?  If not, you may not need to go back that far, no refunds can be issued for years older than 2016.

I recall a case where the wonderful State of California came after a client in the 1980's for a return from the early 1960's. When in doubt FILE THE RETURNS.

So a guy walks into your office and says he hasn't filed since 2010, but wants you to file the returns so that he is clean with the world.  You say ok, let me see your tax documents.  He says, I don't have any.  Don't you just love this job 

 

Yes, I love my job!