My aunt recently found out she became 1/12 owner of a house in 1982 when her husband died. It was his mother's house. The house sold for 0,000 and my aunt received ,500 (1/12) of the proceeds. Her attorney found out the house was assessed at ,800 in 1982. We do not know the market value at the time and since this wasn't her primary residence, she will probably have to pay tax on the gain on the sale, correct? In addition, would she use the assessed value as the cost or inflate it to some number to pay less taxes and come up with a realistic market value. Thanks.