In 2026, overpaying your mortgage usually wins — especially for higher-rate taxpayers. With mortgage rates at 5.2% and best savings rates around 4.7% gross (only 2.82% after 40% tax), overpaying beats saving in most scenarios. Basic-rate taxpayers using a Cash ISA at 4.5% are close to break-even. Always compare your after-tax savings rate to your mortgage rate.
The decision comes down to one comparison:
Your mortgage rate
...is HIGHER than your after-tax savings rate
Your gross savings rate
...beats your mortgage rate after tax (rare in 2026)
The crucial word is after-tax. A savings account paying 4.7% sounds good — but a higher-rate (40%) taxpayer only keeps 2.82% after HMRC takes its share. That's nowhere near a 5.2% mortgage rate.
| Scenario | Effective Return | vs 5.2% Mortgage | Verdict |
|---|---|---|---|
| Mortgage overpayment (5.2%) | 5.2% guaranteed | — | ✅ Benchmark |
| Savings: basic-rate + Cash ISA (4.5%) | 4.5% tax-free | -0.7% | ⚖️ Close call |
| Savings: basic-rate, PSA used (4.7%) | 3.76% after 20% tax | -1.44% | ❌ Overpay wins |
| Savings: higher-rate, PSA used (4.7%) | 2.82% after 40% tax | -2.38% | ❌ Overpay wins clearly |
| Savings: additional-rate (4.7%) | 2.35% after 45% tax | -2.85% | ❌ Overpay wins strongly |
David has £500/month he could either put into a savings account at 4.7% gross or overpay his mortgage at 5.2%.
Sophie is a basic-rate taxpayer with unused Cash ISA allowance. Her ISA pays 4.5% tax-free vs her 4.8% mortgage rate.
Robert is lucky — he's on an old tracker at just 1.9%. His savings account pays 4.5% in a Cash ISA.
Before choosing between overpaying and saving, you must have 3–6 months of essential expenses in an easy-access savings account. This is non-negotiable because:
Use our free calculator to see exactly how much you'd save by overpaying your mortgage — personalised to your rate and balance.
Try the Free Calculator →For most UK homeowners in 2026, overpaying wins — especially higher-rate taxpayers whose net savings return (2.82% after 40% tax) is far below typical mortgage rates of 4.5–5.5%. Basic-rate taxpayers with access to a Cash ISA are close to break-even and may prefer the flexibility of saving.
If your mortgage rate exceeds your Cash ISA rate, overpaying is mathematically better. But the ISA offers flexibility — you can access the money if needed. A common strategy is to build a 6-month emergency fund in an ISA, then overpay the mortgage with any additional surplus.
In 2026, basic-rate taxpayers can earn £1,000 of savings interest tax-free. Higher-rate taxpayers get a £500 allowance. Additional-rate taxpayers get no allowance. Once you've used your PSA, every pound of savings interest above it is taxed at your income tax rate — making overpaying more attractive.