Yes, the unused balance on a HECM reverse mortgage line of credit really does grow each month. But that growth isn’t interest paid to you, it isn’t taxable income, and it isn’t investment yield. Think of it as future borrowing capacity–the kind that compounds at the loan’s current effective note rate plus the 0.50% annual FHA mortgage insurance premium. In mid-2026, with adjustable HECM note rates typically running 6.5% to 7.75%, the combined growth rate on the unused balance sits near 7.00% to 8.25% annually. And FHA insurance under 24 CFR § 206.25 guarantees that growth, blocking any freeze tied to home-value declines, credit-score changes, or lender insolvency. What follows walks through the formula, the math, the FHA protections, and the specific 2026 numbers that shape the calculation.
What the growth rate actually is
The formula’s straightforward. Take the current effective note rate on the HECM, add the 0.50% annual FHA MIP, divide by 12, and apply the result to the unused principal-limit balance each month.
Consider a homeowner with $200,000 of available line of credit at a 7.5% combined growth rate. In month one, the unused balance rises by roughly $1,250. Month two compounds on $201,250, and so on. After 12 months of compounding at 7.5% annually with no draws, the available line reaches roughly $215,540. After 10 years untouched it would sit near $422,700. After 15 years, near $612,900. Those figures assume a steady growth rate, which it won’t be in the real world because HECM note rates are adjustable.
Here’s the practical reality: the mechanic ties directly to how HUD calculates the principal limit over time. Interest and MIP accrue on the outstanding loan balance every month, and the overall principal limit is defined to keep pace, so the unused portion rises at the same rate that costs would have accrued had the funds been drawn. NRMLA’s “Math Behind HECMs” document walks through the underlying equation. Nothing external is being deposited into the account.
What the growth is not
The most common misread of this feature is treating the growth as interest earned. It isn’t. A HECM line of credit is a loan commitment, not a savings vehicle, and the growth represents an increase in how much a borrower can draw later–not cash sitting in an account waiting on a statement.
Because the growth is a change in borrowing capacity rather than a payment received, the IRS doesn’t treat it as income. Reverse mortgage proceeds are treated as loan advances under IRS Publication 936 guidance, so neither the draws nor the paper growth of the unused balance trigger a 1099. Once funds are actually drawn, interest accrues against the loan balance at the standard note rate. That interest becomes deductible only when the loan is repaid, and only within acquisition-indebtedness limits. HELOC interest tax deductibility follows different rules under the TCJA and OBBBA frameworks.
But the growth isn’t free either. Origination fees capped by HUD formula, the 2.0% upfront MIP charged on the Maximum Claim Amount, the 0.50% annual MIP, and third-party closing costs all still apply. Financing those costs into the loan reduces net proceeds at closing.
The 2026 numbers
HUD set the 2026 FHA HECM lending limit at $1,249,125, up roughly 3.26% from the 2025 ceiling. That figure caps the Maximum Claim Amount used to size the principal limit regardless of how much the home actually appraises for above it.
Adjustable-rate HECMs remain the only structure that offers a line of credit. Rate quotes vary by lender and index choice, with most 2026 originations built on the 1-Year CMT or the 10-Year CMT plus a lender margin. Fixed-rate HECMs disburse as a single lump sum at closing and carry no line of credit, so the growth-rate feature doesn’t exist on them.
The FHA guarantee against freeze or reduction
A HECM line of credit can’t be frozen because home values drop, reduced because a borrower’s credit score deteriorates, or cancelled because the servicer or lender fails. FHA insurance backs the borrower’s ability to draw the remaining line for the life of the loan.
So why does that matter for retirement planning? The contrast with traditional HELOCs is what makes the feature valuable. Under Regulation Z § 1026.40(f), lenders may suspend or reduce a HELOC when property value drops significantly, when a borrower’s financial condition deteriorates, or when the lender itself faces impaired standing. Tens of thousands of HELOC borrowers had draw access suspended or cut in 2008 and 2009 (some finding out only when they tried to draw against the line for a repair or a tuition bill) when banks invoked those provisions after the housing crash. See HELOC freeze and reduction rights for the full breakdown of what lenders can and cannot do. A HECM line doesn’t carry that risk because the guarantee sits with FHA rather than the lender.
The catch: the protection is conditional. The borrower must occupy the home as a primary residence, keep property taxes and homeowners insurance current, and maintain the property. And a default on any of those obligations can trigger loan maturity.
The 60% first-year rule
HUD limits first-year draws to 60% of the principal limit, or mandatory obligations plus 10%, whichever is greater. Exceeding that cap at closing triggers a 2.5% upfront MIP instead of the standard 0.5%.
The rule steers many borrowers toward the line-of-credit structure by design. A borrower who wants to leave most of the principal limit undrawn benefits directly, because whatever isn’t taken in year one stays available and compounds at the growth rate. But a borrower who wants the full amount at closing faces the higher upfront MIP and forfeits the growth feature entirely by taking a fixed-rate lump sum.
The standby line of credit strategy
Retirement researcher Wade Pfau has argued in Forbes and the Journal of Financial Planning that opening a HECM line of credit early–at age 62 or shortly after–can function as a sequence-of-returns hedge. The unused balance compounds while equity portfolios ride out market cycles. In a down-market year, some retirees draw from the line rather than sell depressed equities. And in good years, the portfolio recovers and any voluntary repayment restores the drawn balance.
Consider a hypothetical $400,000 available line opened at age 65, untouched, compounding at 7.5% annually. At age 80 the available balance would exceed $1.18 million on that assumption. Worth knowing: the figure is a mathematical projection, not a promise. Growth rates float with the note rate, and the 15-year path is unknowable in advance. The strategy also assumes the borrower still occupies the home and remains current on taxes and insurance.
The line doesn’t lie idle. It rises steadily against a loan document, not a bank statement.
HECM line of credit versus HELOC at a glance
The two products look similar on paper and behave very differently in practice. HECM unused balances grow at the note rate plus MIP, while HELOC credit lines don’t grow at all. HECM draws require no monthly payment while the borrower occupies the home, whereas HELOCs typically require interest-only payments during the draw period and full amortization once the HELOC end-of-draw payment shock begins. HECMs require age 62-plus and HUD counseling; HELOCs use standard mortgage underwriting with no age floor. And HECMs carry FHA non-recourse protection, while HELOCs are full-recourse debt.
Costs and the equity trade
The growth on the unused balance doesn’t cancel the accrued cost on the drawn balance. Every dollar taken from the line begins accruing interest at the note rate plus the 0.50% MIP, and that balance compounds monthly against the home’s equity. Heirs settling the estate face a payoff at maturity that reflects those cumulative charges, offset by FHA non-recourse protection (neither the borrower nor the heirs owe more than the home is worth at payoff, even if the balance exceeds the sale price).
A HECM reduces the equity that passes to heirs. That trade-off is the price of the guarantee and the growth feature, and it deserves plain acknowledgment rather than a soft-pedal.
When the feature doesn’t apply
Fixed-rate HECMs disburse as a single lump sum at closing, so there’s no line to grow. HECM for Purchase transactions–which finance the acquisition of a new primary residence–also disburse in full at closing and offer no growing line. Borrowers who plan to draw the full available principal at closing gain nothing from the growth feature and pay the 2.5% upfront MIP for the privilege. And if rates fall meaningfully after origination, refinancing an existing HECM under HUD’s five-times-benefit rule may be worth reviewing.
Required counseling
HUD requires every prospective HECM borrower to complete counseling with a HUD-approved reverse mortgage counselor before an application can be submitted. The session covers costs, alternatives, and loan mechanics. And the certificate is valid for 180 days.
Frequently asked questions
Is the growth on my HECM line of credit taxable? No. IRS treatment of reverse-mortgage proceeds as loan advances means neither draws nor the paper growth of the unused balance produce taxable income. See IRS Publication 936 for context.
Can my HECM line of credit be frozen if my home value drops? No. FHA insurance protects the borrower’s remaining draw access against home-value declines, though occupancy, tax, and insurance obligations must stay current.
Does the line keep growing if the lender fails? Yes. The FHA guarantee sits with HUD, not the servicer, so servicing transfers and the line remains available.
Do I have to make monthly payments? No. Payments on a HECM are voluntary while the borrower occupies the home, and voluntary repayments restore borrowing capacity and reduce interest accrual.
Does the credit line still grow if I already drew some money? Yes. The growth rate applies to whatever’s left of the unused balance each month. Drawn amounts accrue interest against the loan balance separately.
What happens to the unused line if I move out or die? The loan matures when the borrower no longer occupies the home as a primary residence, and any unused portion ends at maturity. Under HUD’s 2014 non-borrowing spouse rule, a qualifying spouse may be able to defer maturity and remain in the home (specific eligibility conditions apply).
How does HECM line-of-credit growth compare with HELOC interest rates? They aren’t the same measure. HELOC interest rates are what a borrower pays on a drawn balance, while HECM growth is what happens to the undrawn balance a borrower can still access later.
