What does rolled-up interest on a lifetime mortgage cost by age 90?
A lifetime mortgage charges interest that is added to the balance rather than paid, so the debt compounds on itself. At 6% the balance roughly doubles every twelve years — which means the same loan taken at 65 and repaid at 90 costs several times what was borrowed, and the cost is invisible until the estate is settled.
- The mechanism: interest is added to the balance and compounds; nothing is repaid until you die or move.
- The doubling: at 6% the balance doubles roughly every twelve years.
- The protection: the no-negative-equity guarantee caps the debt at the sale proceeds.
- The alternative: voluntary interest payments, which most modern plans allow without penalty.
01 How the balance grows
A lifetime mortgage adds each year's interest to the outstanding balance rather than collecting it. The following year's interest is then charged on the larger figure, and the effect compounds for as long as the plan runs — typically until the last borrower dies or moves into long-term care.
The rule of 72 gives the intuition: at 6% the balance doubles in about twelve years, so £80,000 borrowed at 65 is roughly £160,000 at 77, £320,000 at 89 and more thereafter. Nothing unusual has happened; that is what compounding does over a retirement.
The rate is fixed for the life of the plan under Equity Release Council standards, which removes rate risk and does nothing about the compounding itself.
Shows: what a lifetime mortgage balance grows to by a chosen age, with interest rolled up. Ignores: voluntary payments, drawdown facilities, property growth, and the no-negative-equity guarantee.
On the defaults above, the worked example shows £343,350. Over 25 years at 6% the balance doubles about every 12 years, turning £80,000 into £343,350.
Source: FCA consumer information
02 What limits the damage
The no-negative-equity guarantee means the debt can never exceed the eventual sale proceeds of the property, so beneficiaries cannot inherit a shortfall. That is a real protection and it is a floor rather than a ceiling — it caps the loss at the whole value of the house.
Drawdown lifetime mortgages release money in stages rather than in one sum, so interest only accrues on what has actually been taken. For someone releasing money to supplement income over years rather than for a single purchase, that materially reduces the total cost.
Most modern plans also permit voluntary payments, often up to a defined percentage of the balance each year, without early repayment charges. Paying the interest as it accrues stops the compounding entirely, and it is the single most effective thing a borrower can do.
Source: MoneyHelper: equity release
03 What it does to everything else
Money released is capital in your hands, which means it counts for means-tested benefits. Releasing a lump sum can end a Pension Credit entitlement and the passported benefits attached to it, and those are frequently worth more than the interest saved.
It also reduces the estate, which cuts both ways: less inheritance for beneficiaries, and potentially less Inheritance Tax where the estate was above the bands. Spending the money is what reduces the estate, not the borrowing itself.
And it removes the option to use the house for care costs later. Housing equity is the reserve of last resort for most households, and a lifetime mortgage spends part of it decades in advance — which is worth weighing against the way the means test treats a property that is still owned outright.
Source: Social care charging for care and support 2026 to 2027
Think in doubling periods rather than interest rates, because that is what makes this legible. Six per cent doubles the balance about every twelve years, so borrowing at 65 and dying at 89 means paying back roughly four times what you took. The two things that change the picture are drawdown facilities, which only charge interest on what you have actually released, and voluntary interest payments, which most modern plans allow and which stop the compounding dead. If you can afford the interest, pay it — that single decision is worth more than any rate you could negotiate.
FAQ
How fast does the balance grow?
At 6% it roughly doubles every twelve years, so £80,000 borrowed at 65 is around £160,000 at 77 and £320,000 at 89. The rate is fixed for the life of the plan, which removes rate risk without affecting the compounding.
Can my family inherit the debt?
No. The no-negative-equity guarantee required under Equity Release Council standards means the debt can never exceed the eventual sale proceeds of the property, so beneficiaries cannot inherit a shortfall.
Can I stop the interest rolling up?
Most modern plans allow voluntary payments up to a defined percentage of the balance each year without early repayment charges. Paying the interest as it accrues stops the compounding entirely and is the most effective step available to a borrower.
Sources
Regulator references
- FCA consumer information · Financial Conduct Authority · 2025The regulator's own consumer guidance on the products discussed here.Last verified: 2026-09-07
- MoneyHelper: equity release · MoneyHelper · 2026The government-backed guidance on lifetime mortgages, the standards they follow and their costs.Last verified: 2026-09-07
- Social care charging for care and support 2026 to 2027 · Department of Health and Social Care · 2026The current year's circular, which is where the capital limits are confirmed or changed.Last verified: 2026-09-07
Calculator unit tests · the assertions this page's worked example is checked against, and their last result
Changelog
- 2026-09-07 — initial publish (new format)
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Jordan Reeves
Founder of Talk Through Wealth. A software engineer for over a decade before turning to retirement planning, Jordan built the projection engine after watching family members get fragmented, country-by-country advice that never reconciled. He writes about retirement the way the engine computes it: month-by-month, lifetime-long, and skeptical of any rule of thumb that hasn't been run through the math.