He has been sending 1099-NECs. The 1099-NEC to each person is for 2% of the annual installment amount that he reports as income. The installment income has just been recorded as principal only each year, no interest portion. He does not get a 1099 of any kind. As far as I can tell, the total amount of the sale is reported on his return, which is why the 1099 payments to other people are confusing me. This is all on his personal 1040 return, he is retired and no longer has any business returns. 

I'm sure he has documentation and the sale agreement somewhere. Since the 1099s have not even been reported at all on his returns for the past several years, I'm just trying to get some ideas for where to start or what to even look for before going down this rabbit hole and asking the client for other documentation.