The may be no gain anyway, the cost basis would be what the fair market value of the house was on the date her mom died. It is important that you get in documentation what that amount is. If the property has gone down in value you would not be able to claim a loss because it is your primary residence. Tax would not be paid on the gain if the house is owned for 2 out of the last 5 years by your partner, and the gain (not the selling price) is less than $250,000 ($500,000 for a married couple). Keep in mind (in my opinion) we will probably see completely higher taxes and this benefit (noted above) may disappear under this president and congress.
