How Interest Accrues on a Reverse Mortgage

The most important financial concept to understand before taking out a reverse mortgage is how interest accrual works. Unlike a traditional mortgage where monthly payments keep the balance shrinking, a reverse mortgage balance grows over time because interest compounds on the amount you have borrowed. This growth is predictable and follows well-established mathematical principles -- but the results can surprise borrowers who have not seen the numbers laid out clearly.

The Basics of Compound Interest on a Reverse Mortgage

On a reverse mortgage, interest is calculated monthly and added to your loan balance. The next month, interest is calculated on the new, higher balance. This is compound interest -- you are paying interest on interest.

Your loan balance consists of several components that all accrue interest:

• Principal drawn: The actual cash you have received
• Financed closing costs: Origination fee, initial MIP, and other fees rolled into the loan
• Ongoing MIP: The 0.5% annual mortgage insurance premium added monthly
• Accrued interest: Previously accrued interest that now earns interest itself
• Servicing fee set-aside: If applicable, the amount reserved for servicing fees

Every month, the formula is straightforward: take the current balance, multiply by the monthly interest rate (annual rate divided by 12), add the monthly MIP charge, and that becomes the new balance.

Real-World Accrual Examples

The following scenarios illustrate how a reverse mortgage balance grows over time. These examples use a starting balance of $150,000 (including financed closing costs) at a 6.5% annual interest rate, which includes the 0.5% annual MIP built into the effective rate.

5-Year Scenario

Starting balance: $150,000. After 5 years of compound interest at 6.5%, the loan balance grows to approximately $205,500. The total interest and MIP accrued is roughly $55,500, representing a 37% increase in the balance. Your home needs to appreciate only modestly during this period for you to retain substantial equity.

10-Year Scenario

Same starting balance. After 10 years, the balance grows to approximately $281,700. That is $131,700 in accrued charges -- nearly doubling the original amount borrowed. At this point, whether you retain equity depends significantly on how much your home has appreciated.

20-Year Scenario

After 20 years, the balance reaches approximately $528,800. The loan balance has more than tripled. For a home originally valued at $350,000, you would need the property to have appreciated to at least $528,800 for there to be any remaining equity. At 2% annual home appreciation, the home would be worth approximately $520,000 -- meaning the loan balance could exceed the home's value.

This is where the FHA's non-recourse protection becomes critically important. Even if the loan balance exceeds the home's value, neither you nor your heirs will owe the difference. The FHA insurance fund covers the shortfall.

How Disbursement Method Affects Accrual

One of the most significant factors in how much interest you ultimately pay is how you receive your reverse mortgage proceeds. This is a choice you make, and it has major long-term implications.

Lump Sum: Maximum Accrual

If you take the maximum available amount at closing (required for fixed-rate HECMs), interest begins accruing on the entire balance immediately. Using our example, $150,000 drawn at closing means $150,000 is accruing interest from day one.

Line of Credit: Accrual Only on What You Draw

With a line of credit, interest accrues only on the amount you have actually withdrawn. If you establish a $150,000 line of credit but only draw $30,000 in the first year, interest accrues on just that $30,000 (plus financed closing costs).

Consider this comparison over 10 years:

• Lump sum of $150,000 at closing: Balance grows to approximately $281,700
• Line of credit, drawing $15,000 per year: Balance grows to approximately $170,000 to $190,000 (depending on the timing of draws)

The difference -- roughly $90,000 to $110,000 in less accrued interest -- is substantial. This is one of the primary reasons financial advisors generally recommend the line of credit option for borrowers who do not need all the money immediately.

Monthly Tenure Payments: Gradual Accrual

If you choose tenure payments (fixed monthly payments for as long as you live in the home), the accrual pattern falls between lump sum and conservative line-of-credit use. Each month a new payment is added to the balance and begins accruing interest, but earlier payments have compounded more than later ones.

The Role of Interest Rates in Accrual Speed

The interest rate on your loan dramatically affects how fast the balance grows. Here is how the same $150,000 starting balance looks after 10 years at different rates:

• At 5.0%: Balance grows to approximately $247,300
• At 6.5%: Balance grows to approximately $281,700
• At 8.0%: Balance grows to approximately $330,000

The difference between a 5% and 8% rate over 10 years is approximately $82,700 -- more than half the original loan amount. This is why shopping for the best rate and margin is so important, as discussed in our guide to comparing costs by lender.

Understanding the Equity Equation

Your remaining home equity at any point in time is simply:

Home Value - Loan Balance = Remaining Equity

Two forces are working in opposite directions. Your home (ideally) appreciates in value over time, while your loan balance grows due to interest accrual. If appreciation outpaces accrual, you retain equity. If accrual outpaces appreciation, your equity shrinks and can eventually reach zero.

For borrowers who view their home equity as an inheritance for their children, understanding this dynamic is critical. Having an honest conversation with your family about the trade-offs -- accessing home equity now versus preserving it for later -- is an important step in the decision-making process.

Can You Make Payments to Slow Accrual?

Yes. Although reverse mortgages do not require monthly payments, you are always allowed to make voluntary payments to reduce the balance. Any payment you make reduces the amount of interest that accrues going forward. Some borrowers make periodic interest-only payments or occasional lump-sum payments to slow the growth of their loan balance.

There are no prepayment penalties on HECMs, so you can pay as much or as little as you want, whenever you want. This flexibility can be particularly useful for borrowers who have seasonal income or who receive occasional windfalls.

The Bottom Line

Compound interest is the primary driver of reverse mortgage costs over time, and it can cause your loan balance to grow substantially over a decade or more. The most effective ways to manage this growth are to choose a line of credit over a lump sum, draw only what you need, shop for the lowest interest rate and margin, and consider making voluntary payments when you can. Understanding how interest accrues is not a reason to avoid a reverse mortgage -- it is the key to using one wisely. For a complete picture of what a reverse mortgage costs over its lifetime, see our article on the total cost of a reverse mortgage.