Overpaying Your Mortgage by £200 a Month Saves £27,000 — Here's Exactly How to Do It

Almost every UK fixed-rate mortgage allows overpayments of up to 10% of the outstanding balance per year without early repayment charges (ERCs). On a £200,000 mortgage, that's £20,000 — or roughly £1,667 a month. Most borrowers won't hit that ceiling.

The 10% limit typically resets on your mortgage anniversary, not the calendar year. Check your mortgage offer document (see our mortgage hub for more guidance) — it'll specify the exact terms. Some lenders calculate the 10% on the original loan amount rather than the current balance, which is marginally more generous in the early years.

Tracker and variable-rate mortgages usually have no overpayment limits at all. If you're on your lender's standard variable rate (SVR), you can overpay as much as you like — though if you're on an SVR, remortgaging to a fixed deal is almost certainly a better first move. See <a href="/posts/mortgage-guide-remortgaging-uk-2026-when-to-switch-how-to-compare-deals-and-what-it-costs">when to remortgage and how to compare deals</a> for more details.

Exceed the 10% limit on a fixed deal and you'll face ERCs of 1-5% of the excess amount. On a 5-year fix, early years typically carry higher charges. A £5,000 overpayment above the limit at 3% ERC costs £150 — which may still be worth it depending on your remaining term and rate, but do the maths first.

MoneyHelper has a useful summary of overpayment rules by lender type.

The interest savings from overpaying depend on three variables: your mortgage rate, remaining term, and overpayment amount. Here's what the numbers look like on a £200,000 repayment mortgage with 25 years remaining:

At £200 a month, you clear the mortgage four years early. At £500, you're done seven years ahead of schedule. The savings are front-loaded in a sense — every pound of overpayment in the first five years saves more than the same pound in year twenty, because there's more time for compound interest to work.

Compare this to the alternative. A £200 monthly deposit into a cash savings account at 4% gross (3.2% after basic-rate tax for savers above the Personal Savings Allowance) grows to roughly £12,800 over five years. The mortgage overpayment saves approximately £5,400 in interest over the same five years on a 5% mortgage. But here's the catch — the savings account balance is accessible, while the overpayment isn't (unless you have an offset or flexible mortgage).

The higher your mortgage rate, the more overpaying wins. At 4%, the case is marginal against a good savings rate. At 5%+, overpaying is the clear winner for basic-rate taxpayers.

For the full debate on whether overpaying is the right move, see our case for overpaying and the case against.

Both work. Regular overpayments are easier to budget and create a discipline. Lump sums — from bonuses, inheritance, or savings — make a bigger immediate dent.

The mathematically optimal approach is to overpay as early in the mortgage term as possible. A £10,000 lump sum in year two of a 25-year mortgage at 5% saves approximately £16,000 in total interest. The same £10,000 in year fifteen saves about £4,500. Time is the multiplier.

Some borrowers combine both: a regular £100 overpayment plus an annual lump sum from bonuses. This works well within the 10% annual limit. If your bonus arrives in March but your mortgage anniversary is in September, check whether the 10% window has reset — you might be able to make two lump sums within a few months of each other.

Overpaying isn't always the right move. Five situations where the money is better deployed elsewhere:

1. You don't have an emergency fund. Three to six months of essential spending in an instant-access account comes first. Mortgage overpayments can't be retrieved if you lose your job next month (unless you have a flexible mortgage with a drawback facility — most don't).

2. You have higher-rate debt. Credit cards at 20%+ (see our savings guide for debt vs savings strategies) or personal loans above your mortgage rate should be cleared first. The maths is simple: pay off the most expensive debt first.

3. You haven't used your pension tax relief. A higher-rate taxpayer contributing to a pension (see our pension guide) gets 40% tax relief. That's an immediate 40% return before any investment growth. Even a basic-rate taxpayer gets 20%. Your mortgage rate of 5% can't compete with pension tax relief — especially with employer matching. Check your annual allowance first.

4. Your mortgage rate is below savings rates. If you locked in at 3.5% on a 5-year fix in 2024 and cash savings accounts pay 4%+, the savings account wins on pure numbers. Though remember: savings interest is taxable above the Personal Savings Allowance (£1,000 for basic-rate, £500 for higher-rate), while mortgage interest savings are tax-free.

5. You're approaching remortgage. If your fixed deal ends in six months, consider holding the cash and using it as a larger deposit on the new deal. A lower loan-to-value (LTV) bracket — dropping from 75% to 60% LTV, for example — unlocks better rates that could save more than the overpayment would.

If you want the interest savings of overpaying but hate the idea of locking money away, an offset mortgage solves the problem. Your savings sit in a linked account and reduce the mortgage balance you pay interest on — but you can withdraw them any time.

£50,000 in savings offset against a £200,000 mortgage at 5% means you only pay interest on £150,000. That saves £2,500 a year in interest — and the savings are tax-free because you're not earning interest, you're avoiding paying it.

For higher-rate taxpayers paying 40% on savings interest, offset mortgages are particularly powerful. A 5% savings rate after 40% tax is 3% net. A 5% offset mortgage saves the full 5%. The effective advantage is stark.

The trade-off: offset mortgage rates are typically 0.1-0.3% higher than equivalent fixed deals. On £200,000, that's £200-600 a year — which you need enough savings to offset. The breakeven point is usually around £20,000-£30,000 in savings. Below that, a standard mortgage with occasional overpayments is simpler and cheaper.

See our mortgage hub for rate comparisons and further analysis.

The process is straightforward but varies by lender:

Regular overpayments: Most lenders let you increase your direct debit online or via phone. Some have a dedicated overpayment portal. Nationwide, Barclays, and Halifax all allow online adjustments. Others require a phone call — NatWest and Santander typically need you to call.

Lump sums: Usually done via bank transfer to a specific mortgage account number, or through online banking. Your lender will have a reference number for overpayments. Get this wrong and the money sits in limbo.

Capital vs term reduction: When you overpay, most lenders reduce the term by default — your monthly payment stays the same but you finish sooner. Some let you choose to reduce the monthly payment instead (keeping the same term). The first option saves more interest overall. The second improves monthly cash flow. If you're overpaying to build financial resilience, reducing the payment gives you flexibility — you can always overpay again next month.

Keep records. Screenshot every overpayment confirmation. When you remortgage, your new lender will need an up-to-date balance, and discrepancies between your records and your lender's can delay the process. See our analysis on the case for investing in an ISA instead.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions.