Should you overpay your mortgage in 2026?
An overpayment is a guaranteed, tax-free, risk-free return equal to your mortgage rate. At 5.09% that is better than any savings account available in August 2026 with base rate at 3.75%. The arithmetic is unusually clear, which makes the exceptions worth understanding properly.
In this guide
What an overpayment is actually worth
Take a £220,000 balance at 5.09% with 24 years remaining. The normal payment is £1,325 a month and the total interest over the remaining term is about £161,500.
| Extra per month | Mortgage-free in | Years saved | Interest saved |
|---|---|---|---|
| £0 | 24 years | n/a | n/a |
| £100 | 21 years | 3 years | £23,275 |
| £200 | 18 yr 8 mth | 5 yr 4 mth | £40,409 |
| £300 | 16 yr 10 mth | 7 yr 2 mth | £53,612 |
| £500 | 14 yr 2 mth | 9 yr 10 mth | £72,720 |
Note what £100 a month does: £25,100 of overpayments buys £23,275 of interest saved and takes three full years off the term. Run your own balance on the overpayment calculator.
Overpay or save?
The comparison has to be like for like: your mortgage rate against the after-tax return on savings.
An overpayment at 5.09% is tax free. To match it in a taxable savings account:
- A basic-rate taxpayer needs 6.36% gross
- A higher-rate taxpayer needs 8.48% gross
- An additional-rate taxpayer needs 9.25% gross
No mainstream savings account pays anywhere near those rates in August 2026. Within an ISA the tax disappears, but you would still need 5.09% net, which is above the best cash ISA rates available.
So on pure return, overpaying wins clearly. The genuine counter-argument is liquidity: money in a savings account can be withdrawn tomorrow; money paid into a mortgage generally cannot be recovered without remortgaging. That is a real cost, and it is why the emergency fund comes first, not because the return is better, but because access is worth something.
Overpay or pay into a pension?
For a higher-rate taxpayer this is genuinely close, and pensions often win.
A £1,000 pension contribution costs a higher-rate taxpayer £600 after relief, an immediate 66% uplift before any investment growth. If your employer matches contributions, the return is higher still. Nothing about a 5.09% mortgage competes with that.
The trade-offs: pension money is locked until 57, investment returns are not guaranteed, and 75% of what you eventually withdraw is taxable. For a basic-rate taxpayer without employer matching, the case is much weaker and overpaying is often the better choice.
A reasonable order of priority for most households: employer-matched pension contributions first, then an emergency fund of three to six months of essential spending, then any debt costing more than your mortgage rate, then mortgage overpayments, then additional pension or ISA contributions.
The term-versus-payment trap
This is the detail that quietly destroys most of the benefit, and it catches a lot of people.
When you overpay, the lender can apply it in one of two ways. Reduce the term keeps your monthly payment the same and shortens the mortgage. Reduce the payment keeps the term the same and lowers what you pay each month.
Reducing the term saves substantially more interest, because your full original payment keeps attacking a smaller balance. Reducing the payment feels rewarding, because the direct debit goes down, and saves far less.
Many lenders default to reducing the payment. Tell them in writing which you want, and check your next annual statement to confirm they did it.
Staying inside the allowance
Most fixed-rate deals allow you to overpay 10% of the balance each year with no early repayment charge. Some allow 20%. A few allow nothing at all. Trackers and standard variable rates usually have no restriction.
Two details worth checking on your own offer document:
- Is the 10% based on the current balance or the original loan? On a mortgage that started at £250,000 and is now £180,000, that is the difference between £18,000 and £25,000 of allowance.
- When does the allowance year reset? Usually the anniversary of completion, sometimes 1 January. Getting this wrong by a month can trigger a charge on the whole excess.
Exceed the allowance and the charge is typically 1 to 5% of the excess, depending on how far through the fixed period you are.
When not to overpay
- You have no emergency fund. Overpaying while carrying no buffer means a boiler failure goes on a credit card at 24%. That trade is clearly bad.
- You have higher-rate debt. Credit cards, car finance, personal loans and overdrafts almost always cost more than a mortgage. Clear those first, highest rate first.
- You are a higher-rate taxpayer with employer pension matching available. The relief and match beat 5.09% comfortably.
- Your mortgage rate is very low. Anyone still on a sub-2% deal from 2021 should not be overpaying it, because that money is worth more almost anywhere else.
- You might need the money within two years. Overpayments are generally not recoverable. If a career break, a move or a family change is on the horizon, keep the cash accessible.
Why timing matters more than amount
In year one of a 25-year mortgage, roughly 71% of each payment is interest. By year twenty it is down to about 25%, and in the final year barely 3%. An overpayment made early avoids interest on that money for the whole remaining term; the same overpayment made late avoids only a few years of it.
Practically: £5,000 overpaid in month one of a 25-year mortgage at 5.09% saves around £12,300 in interest. The same £5,000 overpaid in year twenty saves around £1,400. If your overpayment capacity is limited, front-load it.
There is a second timing benefit. Overpaying before a remortgage can drop you into a lower loan-to-value tier, which cuts the rate on the entire balance for the whole of the next deal. If a £1,200 overpayment moves you from 81% to 79% LTV, it may be worth several thousand pounds over a five-year fix. Check your position on the remortgage calculator.
Do this next: model your own overpayment on the overpayment calculator, which shows the years saved, interest saved and whether your plan stays inside the typical 10% allowance.