Refinancing an STL Portfolio in H2 2026: What Lenders Now Ask For That They Did Not Two Years Ago

In short: Around 1.8 million UK fixed-rate mortgages come to an end in 2026, a substantial number held by STL landlords. The criteria applied on remortgage are materially tighter than those applied at original drawdown two, three or five years ago. This is the accounts and evidence pack an STL operator now needs to prepare to get through underwriting cleanly.

Most STL portfolios in the UK were financed against a materially easier lending backdrop than the one their operators will face on remortgage in H2 2026 and 2027. Interest rates are higher. Rental stress tests are harder to pass. The FHL regime that supported the original underwriting has been abolished. And underwriters are asking sharper questions than they were two years ago.

This piece is what we help clients assemble before they approach a broker or lender.

The stress test - and why it fails more often than it used to

The rental stress test is the calculation lenders use to determine how much they will lend. Most mainstream buy-to-let lenders currently stress test at 5.5% or the product rate plus 2%, whichever is higher, and require the rent to cover 125% of that stressed interest for basic-rate taxpayers, or 145% for higher-rate taxpayers.

For a property that was underwritten in 2022 at a 3.5% product rate against 125% ICR, the equivalent 2026 underwriting on a 6% product rate against 145% ICR (for a higher-rate borrower) requires the rent to have grown proportionally. Where it has not - and for many properties it has not - the lender's maximum loan size has fallen. That means either finding equity to pay down the loan on remortgage, or accepting a lower LTV with the accompanying rate uplift.

What lenders now specifically ask for

Beyond the standard bank statements and personal ID, the evidence pack we now routinely prepare for STL clients includes:

Three years of property-level trading accounts. Not the whole portfolio - each property's own P&L, showing booking income, occupancy, and net trading position. Lenders increasingly want to see the specific unit's performance, not just the portfolio average.

Platform payout statements matched to bookkeeping. Where the accountant can hand over booking-level detail from Airbnb / Booking.com / Vrbo reconciled to the tax return, the file moves faster and the underwriter's questions are shorter.

Post-FHL tax computation. For the 2025/26 tax year, lenders want to see the numbers under the new rules, not the FHL rules. Where the client has not filed 2025/26 yet, an accountant-prepared draft tax computation may be required.

Planning status evidence. This is newer. Lenders are increasingly asking whether the property holds planning permission or a Certificate of Lawfulness for the short-term let use. Where the operator's answer is "no" or "not sure", the application is now more likely to be declined, downgraded, or moved to a higher rate. This is why our sister firm STL Solutions recommends addressing planning status well ahead of any refinance.

Confirmation of licence / registration compliance. Scottish STL licence, Welsh register entry (from October 2026), and English register entry (from March 2027 where live).

The two most common refinancing failures we see

Underestimating how much the accounts need to have said last year. Lenders assess against the last set of finalised accounts, not against the operator's projection of what next year will look like. Where the 2024/25 accounts showed a low profit for legitimate reasons - a bad season, capital investment, a change in cost base - that low profit constrains the loan available now, even if 2025/26 will be better.

Assuming an existing lender will renew automatically. They often will not, particularly where the original underwriting relied on the FHL regime, on lower rates, or on a portfolio position that has since changed. Operators who assume the existing lender will roll them over and only discover otherwise weeks before the fixed-rate ends face material stress.

The accountant's role, done properly

A specialist STL accountant supports a refinance in three ways:

1. Preparing the trading accounts pack in a form the lender wants - per-property P&L, reconciled to platform data, aligned to the tax return.
2. Preparing a compliant post-FHL tax computation, ideally with a written explanation of how the year compares to the last FHL year. Underwriters unfamiliar with the FHL abolition sometimes flag the changed treatment as an "unexplained" income drop - a short accountant's note prevents this.
3. Speaking to the broker or lender directly on technical questions. Where a lender's underwriter is unsure how to treat the mortgage interest restriction on a Ltd vs sole trader position, a call from the accountant is often faster than a written response through the broker.

What operators should do now

1. Identify when your current fixed rate ends. If it is inside the next 12 months, start preparation now, not three months out.
2. Model the stressed loan size at 6% / 145% ICR against your current rental income. If the number is lower than your current loan balance, the delta is your equity requirement.
3. Address any weak spots in the accounts before applying. Retroactive fixes are limited but not zero.
4. Get planning status onto a defensible footing before underwriting. This is now a live underwriting question, not a nice-to-have.
5. Speak to a specialist STL accountant well before speaking to the broker. The evidence pack takes time to assemble properly, and preparing it after the broker's asked for it is much harder than preparing it in advance.

Refinancing an STL portfolio in H2 2026 is a materially different exercise from the one operators did five years ago. The difference is not that lending has disappeared - it has not. The difference is that the evidence bar has moved up and the operators best placed to clear it are the ones who prepared before they were asked.

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