One of my favorite stories. 20 years ago TP(?) new client walked into my small town office & said he needed to file for SS. I suggested that he go to SS office in the city since he has already paid them for that service. He indicated that he had, but they wanted his last 3 years returns. I said so? He says he hasn't filed last three years. I ask when did he last file. He says NEVER. Seems he left the navy after WWII, bought a truck & equipment & earned a living for 40 years painting farm buildings for cash. Never filed a return. I prepared 3 returns using "best evidence available" & he collected SS til he died 15 years later.