Buy-to-Let Remortgage Calculator: New Payment, Savings, Fees & Rent Cover

A remortgage only pays off once the fees are covered. The headline rate tells you the new payment, not whether switching is worth it once the product fee, valuation, legal work and any early repayment charge (ERC) for leaving the old deal are counted. This calculator turns your current payment and the new deal’s numbers into the new payment, the monthly and total saving over the new deal, the break-even point on the fees, and — because a remortgage is underwritten like a fresh purchase — the rent-cover test, the maximum loan the rent supports, and the LTV.

Two ways to pay the product fee

Most remortgages carry a product fee, typically £1,000–£2,000 (Uswitch, 2026). Lenders usually let you add it to the loan instead of paying cash at completion — but you then pay interest on it for the rest of the term, which this calculator reflects by basing the new payment on the higher, fee-inclusive balance whenever “add to the loan” is chosen. Paying upfront keeps the balance, and the payment, lower. Both are shown so you can compare them rather than assume either is free.

What counts as a switching cost

Valuation and legal fees are almost always cash, not added to the loan, and on a remortgage are often waived entirely as an incentive to switch: Uswitch puts a typical valuation at £300–£500 (up to £1,500 for an unusual property) and legal work at around £300 — far below a purchase’s roughly £2,000 (see the purchase cost calculator), since there’s no chain. The ERC for leaving early can dwarf the rest: commonly 1–5% of the balance, so £200,000 owed could mean £2,000–£10,000 to leave — check your mortgage offer, since it usually shrinks nearer the end of the fixed term. This tool treats valuation, legal and the ERC as cash at completion, and only the product fee as optionally financed, matching how lenders structure it.

Break-even: when does the switch pay for itself?

If the new rate lowers the payment, the switching costs are a one-off the saving gradually repays: break-even is the cash fees divided by the monthly saving, rounded up to a whole month. Compare that to the new deal’s length (commonly 2–10 years, per Uswitch) to see if it has time to earn its keep. If the new rate is higher, there’s no saving to break even with — see the remortgage payment shock calculator for that case, including the Section 24 effect on the extra interest.

The rent-cover test still applies

A remortgage is underwritten like a purchase: rent has to cover the mortgage interest, at a stressed rate rather than the pay rate, by a margin. This reuses, unchanged, the mechanics this site’s own buy-to-let mortgage stress test publishes — a stress rate of the higher of 5.5% or the new rate plus 2 points, and a rent-cover requirement of 125% for a basic-rate taxpayer or limited company, up to 145% for a higher-rate taxpayer. Maximum loan and LTV use the same stressed rate, so you see both the real cost and whether the lender will actually offer it.

Worked example

£180,000 owed, paying £850 a month now, remortgaging interest-only at 5.5% with a £1,500 fee paid upfront: the new payment is £825 — £25 less. Over a 5-year deal that’s £1,500 of saving, exactly what the fee cost — a 60-month break-even and, on the numbers alone, a wash. But at a stress rate of 7.5% (the new rate plus 2 points, above the 5.5% floor) and £1,400 rent, cover is only about 124% — just short of the 125% a basic-rate taxpayer or limited company needs. The maximum this rent actually supports at 125% ICR is about £179,200 — £800 short of the £180,000 asked for, even though the loan sits at exactly 75% LTV against a £240,000 valuation. A real application here would likely be trimmed slightly, exactly the gap this tool is built to surface before you apply.

What this figure is, and isn’t

This is a planning calculation, not a mortgage offer or a decision in principle — a real lender may price the ERC, fee or stress rate differently. Scottish and Welsh taxpayers use the same UK-wide lending conventions modelled here; what differs by nation is the tax band the extra or saved interest is measured against — see the rental income tax calculator, the Section 24 explainer, and buy-to-let mortgage rates explained for how lenders price the deal itself.

ICR / stress-rate / LTV mechanics: Property Filter, “Buy-to-Let Stress Test: The Complete Guide for UK Property Investors” (page states “Last updated: 19 Nov 2025”), read 13 Sep 2026 — the same convention already used on this site’s buy-to-let-mortgage-stress-test.html and remortgage-payment-shock-calculator.html. Remortgage fee figures (product fee, valuation, legal, ERC, typical deal length): Uswitch, “How Much It Costs To Remortgage In 2026” (edited by Jason McDonald, 23 October 2025), read 13 Sep 2026. These are lending-market conventions and costs, not statutory rates or a lender’s underwriting decision — they change with the market and by product. General information, not advice.