The short answer.
For most people with a standard repayment mortgage at a typical UK rate, regular overpayments make a meaningful difference and are usually a good idea. But not always — and not as the first call on your money. There's an order that almost always makes sense.
The order of priorities.
Pay off expensive debt first.
Credit cards at 24% APR, store cards, payday loans. Your mortgage rate is rarely above 6%. Paying down higher-interest debt always wins — by a lot.
Build an emergency fund.
Three to six months of essential outgoings, accessible (an easy-access savings account, not locked away). Once that money goes into your mortgage, you can't get it back without remortgaging.
Get full pension matching from your employer.
If your employer matches 5% of pension contributions and you're only contributing 3%, you're leaving free money on the table. Capture every penny of match before you overpay anything.
Then overpay your mortgage.
Once the above is sorted, mortgage overpayments are usually the most efficient next step — particularly while rates are above historic norms.
Why overpaying works.
Every pound you overpay reduces the balance the lender is charging you interest on. Over a 25-year mortgage, that compounds dramatically.
Worked example: £200,000 mortgage at 4.5%, 25 years
No overpayments: Monthly payment £1,112 · Total interest paid: £133,499 · Term: 25 years.
£100/month overpayment: Total interest paid: £112,358 · Term: 21 years, 6 months.
You save £21,141 in interest and finish your mortgage 3½ years early — for £100 a month.
£250/month overpayment: Total interest paid: £91,135 · Term: 17 years, 10 months.
You save £42,364 and finish over 7 years early.
The 10% rule.
Most fixed-rate mortgages let you overpay up to 10% of the outstanding balance per year without an early repayment charge (ERC). Go above 10%, and the ERC bites — typically 1–5% of the amount above the limit.
For most overpayers this isn't a constraint. 10% of a £200,000 mortgage is £20,000 a year — £1,667 a month — which is well above what most people will sensibly overpay. But if you've come into a windfall (inheritance, bonus, sale of a business), check your specific deal's terms before throwing it at the mortgage.
Lump sum or regular overpayments?
- Regular overpayments
Smoother on cash flow, easier to commit to, and most lenders let you start, stop, or change them online in seconds. Best for "I want to chip away at this consistently."
- Lump-sum overpayments
Bigger immediate impact on the balance and on the interest saved. Best for "I've got £8,000 sitting in a savings account doing nothing useful."
You don't have to choose — many borrowers do both: a small monthly overpayment plus the occasional lump sum from bonuses or tax refunds.
Reduce the term, or reduce the monthly payment?
When you overpay, most lenders ask whether you'd prefer the overpayment to shorten the term or reduce the monthly payment.
- Shorten the term
Bigger total interest saving, but your monthly commitment stays the same. Better if you can comfortably afford the current payment and want the mortgage gone.
- Reduce the monthly payment
Frees up cash flow each month. Less interest saving overall but more flexibility if your circumstances are uncertain.
You can usually change this with a phone call if circumstances change. Default is shorten-the-term for most lenders, which is also usually the better choice — but make sure you've actively chosen, rather than drifted into it.
When overpaying isn't the best move.
- You've got a very low fixed rate
If you're still on a sub-2% deal from 2021, you're paying less to the lender than a competitive savings account is paying you. Keep the cash in savings and overpay at the end of the fix.
- You don't have a Lifetime ISA (and you're under 40)
If you're saving for a future house move and you're under 40, a LISA gets you a 25% government bonus on £4k a year. That beats almost any mortgage overpayment maths.
- You have an offset mortgage
An offset mortgage lets your savings effectively work against your mortgage balance without losing access to the cash. If you have an offset, fund the offset before considering a direct overpayment — same interest saving, but with the safety net of being able to take the money out again.
- You're planning to remortgage soon and might want to borrow more
If you're going to capital-raise on remortgage (say, for an extension), there's little point reducing the balance now only to add it straight back on.
One question worth answering honestly.
"If I overpay £200 this month, will I still feel comfortable in three months?" Overpayments only make sense if they're sustainable. Stretching to overpay, then having to borrow on a credit card a month later because something unexpected came up, undoes all the maths and then some.
How to actually do it.
Log into your lender's online portal.
Almost every UK lender now lets you set up overpayments online — Halifax, Nationwide, Santander, NatWest, Barclays, the lot. Look for "make an overpayment" or "change my payments."
Pick monthly or one-off.
Both options are usually right there. You'll be asked whether to shorten the term or reduce the monthly payment (see above).
Set up the standing order.
For regular overpayments you may need to set up a separate standing order from your bank — your existing direct debit is for the contractual payment. The lender will tell you the reference to use.
Check the impact after the first month.
The next mortgage statement should show the overpayment applied. If it hasn't reduced the balance, ring the lender — occasionally an overpayment is wrongly treated as advance payment of future months.
Your home may be repossessed if you do not keep up repayments on your mortgage. This guide is general information, not personal mortgage advice. For advice on your specific situation, book a free chat.