England's first-time buyer stamp duty relief is worth a flat £5,000 to anyone buying a main residence between £300,000 and £500,000 — the same cash saving at £310,000 as at £490,000. Homecost previously measured that relief against an interest-only mortgage and found it shrinks from 6.2 months of interest at £300,000 to 3.7 months at £500,000. But most first-time buyers don't take interest-only mortgages — they take standard capital-repayment ones, where the monthly payment covers both interest and paying down the loan itself. Redone against a realistic 25-year repayment mortgage at the Bank of England's most recently quoted rate, the same £5,000 covers noticeably less: 4.1 months at £300,000, falling to 2.4 months by £500,000.
The relief in months of a real mortgage payment
| Purchase price | 75% LTV loan | Monthly payment (25-year repayment, 4.32%) | First-time buyer relief | Relief, in months of payment |
|---|---|---|---|---|
| £300,000 | £225,000 | £1,228 | £5,000 | 4.1 |
| £350,000 | £262,500 | £1,432 | £5,000 | 3.5 |
| £400,000 | £300,000 | £1,637 | £5,000 | 3.1 |
| £450,000 | £337,500 | £1,842 | £5,000 | 2.7 |
| £500,000 | £375,000 | £2,046 | £5,000 | 2.4 |
| £500,001 | £375,001 | £2,046 | £0 | 0.0 |
Monthly repayment figures assume a 75% loan-to-value mortgage repaid over 25 years at the Bank of England's quoted 5-year fixed rate of 4.32% (April 2026 print, still the most recent published at the time of writing) — a standard capital-and-interest amortisation, not interest-only. Stamp duty figures were checked against Homecost's stamp duty calculator on 15 September 2026: a first-time buyer pays £0 at £300,000, £5,000 at £400,000 and £10,000 at £500,000, against a £15,000 bill the moment the relief disappears above £500,000.
Why the repayment figure is smaller, not larger
A repayment mortgage's monthly payment is always higher than an interest-only payment on the identical loan and rate, because part of every payment reduces the loan balance rather than just servicing the interest on it. Dividing a fixed £5,000 by a larger monthly figure produces a smaller number of months, not a bigger one:
| Purchase price | Relief, in months of interest-only payment | Relief, in months of 25-year repayment |
|---|---|---|
| £300,000 | 6.2 | 4.1 |
| £350,000 | 5.3 | 3.5 |
| £400,000 | 4.6 | 3.1 |
| £450,000 | 4.1 | 2.7 |
| £500,000 | 3.7 | 2.4 |
The shape of the pattern is the same either way — the relief buys a shrinking number of months as price rises through the £300,000–£500,000 band, then nothing at all above it, as Homecost has set out in full. What changes between the two mortgage types is the size of the yardstick the £5,000 is being measured against, not the underlying tax mechanics: HMRC applies exactly the same relief regardless of how a buyer chooses to structure their mortgage.
How many buyers this band actually affects
The £300,000–£500,000 taper is not a niche slice of the market. Of 758,160 category-A residential sales recorded by HM Land Registry in England during 2025 (checked 15 September 2026):
| Price band | Share of 2025 English sales |
|---|---|
| £300,000 or less (relief covers the full stamp duty bill) | 50.2% |
| £300,001–£500,000 (relief worth a shrinking number of months) | 30.8% |
| Above £500,000 (relief withdrawn entirely) | 18.9% |
Just under a third of England's residential sales in 2025 fell inside the band where this erosion plays out — and it applies however the buyer chooses to finance the purchase.
What this doesn't tell you
This is a comparison of tax and mortgage arithmetic, not advice on which mortgage product to choose or a claim about the rate any individual buyer will secure. Real mortgage rates depend on the lender, deposit size and credit profile, and will differ from the Bank of England's quoted average used here. A 25-year term and 75% loan-to-value are common starting assumptions, not universal ones — a longer term lowers the monthly repayment (and raises the months-of-relief figure); a larger deposit lowers the loan size and does the same.
This analysis draws on Land Registry sale records and Homecost's own stamp duty and mortgage-rate data — see more data-led analysis in Homecost's cost intelligence guides.
Try the calculation on a real purchase price with Homecost's mortgage calculator, or see the fuller cost picture — mortgage, council tax and stamp duty together — for a property by looking up a postcode such as Manchester's M1 1AE on the true-cost tool.
This is general information about how stamp duty relief and mortgage repayments are structured, not advice on whether or how to buy. Speak to a qualified adviser before acting.