You cannot deduct the interest that accrues on a reverse mortgage until it is actually paid, which doesn’t happen until the mortgage is paid off in full. At that time, the mortgage interest usually is subject to the limitation for home equity debt.
Debt secured by a principal residence or second home to the extent of the excess of fair market value over acquisition debt. An interest deduction is generally allowed for home equity debt up to $100,000 ($50,000 if married filing separately).