Its fairly complicated. The issue is how much gain did you have on your house. You bought it for $50,000 with a sale at $310,000, then, potentially, you have a $260,000 gain. You can (as a single filer) deduct a $250,000 gain on your principal residence ($500,000 if married). Your are limited by years of occupancy, previously taking the exclusion (see: https://www.irs.gov/taxtopics/tc701). You can also reduce your gain by the cost of sale (realtor fees, sales tax or equivalent). The fact that you had a reverse mortgage that might mean that your take on the house was small at sale, is not relevant to how it is handled for tax purposes. Mortgage payoff is not part of the tax calculation.
