Buy-to-let remortgages

The six-month window

Most buy-to-let lenders let you secure a new offer up to six months before your existing rate ends. You hold the offer, watch the market, and re-broke if a cheaper rate appears. If rates rise, you have already locked in. The downside is small, the upside is the cost of a few weeks of broker effort.

Why the SVR hurts on a buy-to-let

The SVR (Standard Variable Rate) on a buy-to-let is often two to four percentage points above mainstream new-business rates. On a £200,000 buy-to-let interest-only mortgage, that can be £300 to £600 a month for nothing. The lender is not the bad guy, you simply did not switch in time.

How buy-to-let stress tests differ

Lenders test the rent against a stressed interest rate. The ICR (Interest Cover Ratio) requirement varies by tax band, with most lenders wanting rent to clear 125% to 145% of stressed interest. Higher-rate taxpayers face higher ICR requirements because Section 24 leaves them with more tax to pay on the rent. Limited company cases often have a lower ICR threshold than personal-name cases.

Worked example, ICR test on a £180,000 buy-to-let remortgage

Outstanding mortgage £180,000, property valued £260,000 (69% LTV). Rent £1,200 a month (£14,400 a year). Higher-rate taxpayer in personal name, lender stress at 5.5%, ICR required 145%. Annual stressed interest £9,900. ICR-required rent £14,355; case clears with £45 a year of headroom, tight. Same case in an SPV (Special Purpose Vehicle): lender stress 5.5%, ICR 125% (corporate rule). Required rent £12,375; case clears with £2,025 of headroom, comfortable. Same property, same rent, same loan, but the ownership structure decides which lenders quote and what borrowing is achievable. We pick the lender whose stress test fits.

Product transfer versus remortgage

If you stay with your existing lender on a product transfer (a new fixed rate from your current lender without a full re-underwrite), the timeline is faster (often 1 to 2 weeks), the documentation is lighter, but the rate is rarely the best in market. A full remortgage to a new lender takes 6 to 10 weeks but usually wins on price. We compare both before recommending.

Releasing equity at remortgage

If your property has appreciated, the remortgage is a good time to release capital for the next deposit. The new ICR will be calculated on the higher loan, so you will need a stronger rent to support the additional borrowing. We model the headroom before applying. Common pattern: a property bought 5 years ago at £200,000 with £150,000 mortgage is now worth £240,000; remortgage at 75% LTV pulls the loan up to £180,000, releasing £30,000 toward the next deposit, with the new ICR holding because rent has risen alongside.

Stress-rate environment in 2026

Lender stress rates have been moving with Bank rate. As of 2026, typical stress rates sit at 5.5% to 7% depending on lender, product type and tax band. Some lenders apply a lower stress rate (around 4.5% to 5%) on 5-year fixed products on the basis that the borrower is locked in for longer, which often makes 5-year fixes the only way the case clears. We map the lender stress rate to the case before applying.

Common pitfalls we see

Letting the rate end and falling onto the SVR while paperwork catches up. Picking a lender whose ICR rule fails the case when a peer lender on a different rule would clear. Releasing more equity than the new ICR will support and getting an offer at a smaller release. Not refreshing the rental valuation when local rents have moved. We mind all four.

Buy-to-let warning

Most buy-to-let mortgages are not regulated by the Financial Conduct Authority. Switching products on a buy-to-let does not give you the same Consumer Duty protections as a residential remortgage. Take that into account when comparing routes.