Should you save your extra money or overpay your mortgage? Compare the guaranteed return of mortgage overpayment against savings account interest rates.
The comparison hinges on your after-tax savings return versus your mortgage rate. The mortgage return is guaranteed and risk-free; savings returns are also low-risk but subject to tax.
| Mortgage Rate | Break-even Gross Savings Rate (Basic 20%) | Break-even Gross Savings Rate (Higher 40%) |
|---|---|---|
| 3.5% | 4.375% | 5.833% |
| 4.0% | 5.000% | 6.667% |
| 4.5% | 5.625% | 7.500% |
| 5.0% | 6.250% | 8.333% |
| 5.5% | 6.875% | 9.167% |
It depends on interest rates. If your after-tax savings rate exceeds your mortgage rate, saving is mathematically better. If your mortgage rate is higher (common in 2025/26 with rates around 4–5%), overpaying delivers a guaranteed tax-free return equal to your mortgage rate. For most people with mortgages above 4%, overpaying beats most easy-access savings accounts after tax.
Yes. Every pound you overpay reduces your outstanding mortgage balance immediately. Future interest is calculated on the lower balance. A £200/month overpayment on a £200,000 mortgage at 4.5% with 20 years remaining could save over £15,000 in interest and shorten the term by around 3 years.
Most UK lenders allow overpayments of up to 10% of the outstanding balance per year without early repayment charges. This limit resets annually. Always check your specific mortgage terms, as tracker and variable rate mortgages often have no overpayment limit.
In 2025/26, basic rate taxpayers can earn up to £1,000 in savings interest tax-free. Higher rate taxpayers get a £500 allowance. Additional rate taxpayers get no allowance. Interest above these amounts is taxed at your marginal rate. ISA interest is always tax-free.
For a higher-rate taxpayer with a 4.5% mortgage, they need a savings rate of 4.5% / (1 − 0.40) = 7.5% gross to break even. For a basic-rate taxpayer, they need 4.5% / (1 − 0.20) = 5.625%. Below the Personal Savings Allowance, the gross rate is the break-even point.
Some flexible mortgages allow you to redraw overpayments later. However, most standard repayment mortgages do not — once you overpay, that money is locked in. Always check your mortgage terms. If you might need access to the money, keeping it in savings offers more flexibility.
Yes. Reducing your mortgage balance improves your Loan-to-Value ratio. If overpayments drop your LTV from 80% to 75% or below, you may qualify for lower mortgage rates on your next fix — potentially saving £2,000–£5,000+ over a 2-year fix.
Mortgage overpayment gives a guaranteed, risk-free return equal to your mortgage rate. Stock market investment offers higher expected returns (7–9% annually) but with significant volatility. Most planners suggest: clear high-interest debts first, then consider investing if your mortgage rate is below 4%.
An offset mortgage links your savings to your mortgage. Instead of earning interest on savings, you reduce the mortgage interest charged. If you have £20,000 savings offset against a £200,000 mortgage at 4.5%, you only pay interest on £180,000. The effective return equals your mortgage rate, tax-free.
Pension contributions often win for higher-rate taxpayers due to 40–45% tax relief. The effective return on a pension contribution for a 40% taxpayer is a 67% instant return (you pay in £600, government adds £400). Overpaying mortgage typically beats standard savings but rarely beats pension contributions for higher earners.
Yes. Lenders price mortgages in LTV bands. Crossing a lower threshold — say from 76% to 74% — can unlock the 75% LTV rate tier, which often carries a meaningfully lower rate. A targeted overpayment to cross a threshold can be very valuable.
Most UK lenders apply overpayments to reduce the outstanding balance, which can either shorten the term or reduce future monthly payments. Many lenders default to shortening the term (saving more total interest). Contact your lender to specify your preference.