Land contract vs seller mortgage and capital gains

[Account Closed]

I am trying to structure a deal with a seller for owner financing. We have the numbers worked out and he was going to do a seller note and hold a mortgage. His accountant has told him that it would have to be a land contract to defer capital gains taxes. I cannot find information to confirm this. The issue is everything says "installment sale" and I don't know if that includes mortgages.

Any ideas?