You will pay tax on the entire gain. There is no proration of anything for you. In order to qualify for the capital gains tax exclusion, or any part of it, the property must have been your *primary* residence for at least 2 years of the last five years you owned it, counting back from the closing date of the sale. Since the property has been a rental since 1996 or 97, you don't even come close to qualifying normally, or under any of the exceptions either.
