Should I overpay my mortgage or put the money into savings?

Whether it is better to overpay your mortgage or keep spare money in savings depends on the mortgage interest you could avoid, the savings interest you would actually keep, and how much access you need to your cash. A savings account with a higher rate may be worth more financially, but an overpayment can be valuable if your mortgage costs more. Neither conclusion is automatic: tax, penalties and future rate changes matter.

Start with the cash you might need back

Mortgage overpayments usually reduce your outstanding loan, but getting that cash back is not as simple as withdrawing from an easy-access savings account. Before comparing rates, consider an emergency fund and any higher-interest borrowing. MoneyHelper’s mortgage overpayment guidance recommends retaining an emergency reserve, checking expensive debts first and reviewing the mortgage terms. Your lender may have different rules for flexible or offset mortgages.

Compare the same amount over the same period

For a fair comparison, start with the same mortgage balance, remaining term and spare cash. In the savings scenario, keep paying the usual mortgage instalment and add your spare money to savings. In the overpayment scenario, put that same spare amount against the mortgage each month. Compare savings minus the remaining mortgage balance on the same date, rather than comparing interest figures alone.

For example, assume a £200,000 repayment mortgage, 25 years remaining, no lump sum, and £200 extra available at the end of each month for five years. The mortgage rate and savings AER stay unchanged, all savings interest is tax-free, and there are no overpayment fees. The example uses the site’s monthly mortgage-interest model and an effective monthly savings rate derived from AER; actual lenders may calculate interest daily.

Example A: 4.5% mortgage and 4% tax-free savings AER

Try the worked examples yourself: Load example A: 4.5% mortgage and 4% tax-free savings, or load example B: 4% mortgage and 5% tax-free savings. The calculator opens with the same £200 monthly contribution, 25-year repayment term and five-year horizon. These are illustrative rates, not live offers.

Saving £200 each month produces about £13,235.80 after five years. Directing the same payments towards the mortgage reduces the balance by about £13,429.11 more than the standard repayment schedule. On these assumptions, overpaying leaves your net position about £193.31 better at the five-year comparison date. That does not mean the interest saved is £13,429.11: most of that figure is your £12,000 in extra payments, plus the interest effect.

Example B: 4% mortgage and 5% tax-free savings AER

With the same mortgage balance, term and £200 monthly contribution, savings reach about £13,562.75 while the additional mortgage balance reduction is about £13,259.80. Savings finish ahead by about £302.95. These are illustrative fixed-rate scenarios, not current provider offers or predictions of rates five years ahead.

Try different assumptions in the savings versus mortgage overpayment calculator. You can include an upfront lump sum and estimated tax treatment, then compare projected net positions at a chosen date.

Compare savings interest after tax, not just the headline rate

Interest earned outside an ISA can be taxable. HMRC’s savings tax guidance explains the Personal Savings Allowance: typically £1,000 for basic-rate taxpayers, £500 for higher-rate taxpayers and £0 for additional-rate taxpayers. Other income, unused Personal Allowance and the starting rate for savings can change the actual result; your tax band is determined using savings interest as well as other income. The allowance operates by UK tax year (6 April to 5 April), not by the anniversaries of your mortgage comparison.

Interest on cash in an eligible ISA is normally free of UK Income Tax, subject to account and subscription rules; check GOV.UK’s ISA guidance. If modelling tax-free ISA interest in the comparison calculator, use a zero savings tax rate. If modelling taxable interest, enter a realistic tax rate and unused allowance, remembering that the calculator applies a simplified 12-month tax estimate. Use the Personal Savings Allowance calculator for an initial estimate, and read our guide to savings tax allowances for important exclusions.

When does saving make more sense?

Accessible savings can provide a cushion for unexpected bills, a job change or a mortgage deal ending soon. It may be financially favourable if the interest you actually keep is higher than the mortgage interest avoided, but check whether the account’s rate is variable, whether withdrawals are restricted and whether a temporary introductory rate is involved. For savings interest credited on different schedules, see our guide to daily interest and compounding.

When might overpaying make more sense?

If your mortgage costs more than the after-tax savings return, an allowed overpayment can reduce the balance and the interest charged later. Whether it shortens the term or changes the monthly payment depends on your lender’s arrangements. Before moving money, check your mortgage statement for annual penalty-free overpayment limits and any early repayment charge. A fixed-rate mortgage can impose costs if you exceed its limits; do not assume a percentage cap is universal.

If you’re approaching a new deal, use the mortgage balance at renewal calculator to understand the projected outstanding balance and the mortgage repayment calculator to explore different payment assumptions.

A practical decision checklist

1. Keep an emergency reserve you can reach without borrowing.
2. Check whether more expensive debts should take priority.
3. Confirm the overpayment allowance, penalty and how your lender applies extra payments.
4. Compare a realistic savings AER after estimated tax, fees and access restrictions.
5. Run the same contributions and time horizon in both scenarios; test a higher and lower future rate.
6. Review the decision if your mortgage deal, savings rate or circumstances change.

Limits of the calculator and review information

The calculator assumes fixed mortgage and savings rates, a monthly repayment schedule and simplified savings tax calculated in twelve-month blocks. It does not model early repayment charges, individual lender rules, offset mortgages, provider fees, daily mortgage interest timing, changing tax law or your entire savings-tax position. Treat a small modelled difference as a prompt to compare real account and mortgage terms, not a personal recommendation.

Editorial review: 30 October 2026. We checked the cited MoneyHelper and GOV.UK guidance and independently calculated the two five-year examples using the documented monthly assumptions. This review does not certify future rates, provider terms or individual tax eligibility. Official references: MoneyHelper, HMRC and GOV.UK ISAs.