Had installment sale of house and land, it was repossessed and now used as rental in corporation. I figured the new basis, balance of installment sale but where do I post the difference. Example - balance a/r installment sale $100,000, basis of reposed property to be used as rental - $20,000. Where do the remaining $80,000 go since it will be a profit to the corp.

You are missing unrealized gross profit, cost of instalment sales as well as the estimated market value on the date of repo.