After you file

yes you need to amend. there was probably no specific question about the sale of a second house but there would have been a question about other income.  there is no specific 2nd home sale worksheet. you would use the 1099-B worksheet - type E if a 1099-S was issued or type F if there wasn't.. enter dates description sales proceeds and cost (including sales expenses). a loss isn't deductible so you would need to limit the cost to the sales proceeds. this assumes that the home was never rented and no depreciation was ever taken on it