For portfolio landlords, profitability on paper does not always mean there is cash readily available. Higher mortgage payments and rising property costs in 2026 can quickly reduce the amount left in the bank each month regardless of rental income, and pressure can build further when a major repair coincides with a void period, or when several fixed-rate buy-to-let (BTL) mortgages are due to end around the same time.
Effective rental cash flow management starts with understanding when future costs are likely to arise and whether the portfolio’s borrowing structure still supports the landlord’s longer-term plans.
Review each property separately
Looking only at total rental income can hide weaker properties within a portfolio. One property may produce a reliable surplus, while another may be absorbing cash because of its mortgage costs. A property may also have risen significantly in value without contributing much to monthly income. Each property should therefore be reviewed on its own, comparing the rent received against the mortgage payment and regular running costs, while also allowing for maintenance and periods when the property may be empty.
The date of the next mortgage change should be recorded, along with the property’s current value and available equity. This review can show which properties are supporting the portfolio and which are placing pressure on it. It may also help landlords decide whether a property needs refinancing or whether a sale should be considered.
Plan for future mortgage payments
The current monthly payment only tells part of the story, particularly where several fixed-rate deals are due to end within the next two years. Modelling repayments at higher interest rates can help landlords understand how much pressure this could place on the portfolio and whether changes may be needed before any of the mortgages reach their expiry dates.
Lenders usually assess buy-to-let affordability using the interest coverage ratio, known as ICR, which compares rental income with mortgage interest. Passing this calculation does not necessarily mean the property will generate the level of surplus the landlord needs, so any cash flow forecast should also reflect the actual cost of running the property.
Look at borrowing across the portfolio
Refinancing each property in isolation can lead to decisions that suit one mortgage without supporting the wider portfolio, which is why it is worth reviewing how debt is structured across all properties and whether available equity could be used more effectively.
Reducing the mortgage on a property with weaker rental coverage may improve the range of lender options available, while releasing equity elsewhere could help fund essential work or build a stronger cash reserve. Any additional borrowing still needs to be considered carefully, as improved access to cash in the short term may come with higher monthly payments and a greater overall debt burden.
The priority is to understand the effect of any change across the portfolio before proceeding.
Start remortgaging early
Cash flow pressure becomes harder to manage when a mortgage deal is close to ending, so starting the refinancing process early gives landlords more time to compare lenders, arrange any valuation work and address concerns around rental coverage before an application is submitted.
This may involve choosing between a product transfer with the current lender and a full remortgage elsewhere. A product transfer can be more straightforward and may involve lower fees, while a remortgage could provide access to a different rate or allow the borrowing to be adjusted. The right route will depend on the property and what the landlord needs the mortgage to achieve.
The market is currently being shaped by refinancing rather than new purchases. UK Finance data for the first quarter of 2026 shows buy-to-let remortgages rose 11.1% year-on-year to 39,160 loans, even as lending for house purchase fell by almost 15%. That trend is driven disproportionately by portfolio landlords: research from Paragon’s Landlord Trends survey found 56% of those holding four or more mortgages plan to remortgage within the next 12 months, compared with 24% of landlords with one to three properties, and expect to refinance an average of 2.7 loans each. With so many BTL deals maturing at once, lenders and valuers are busy, so I would always encourage clients to begin the remortgage conversation around six months before a fixed rate ends. That lead time is what allows us to test rental coverage against current interest coverage ratios, weigh a product transfer against a full remortgage, and act before a deal reverts to a lender’s standard variable rate.
Keep a cash reserve
Property may be a long-term investment, but many of the costs involved need to be covered immediately, whether that is an urgent repair or a longer-than-expected void period that reduces rental income.
Holding a dedicated cash reserve can help landlords manage these pressures without having to rely on expensive short-term borrowing. The amount required will depend on the portfolio, with older properties often needing a larger buffer because repairs can be less predictable, while flats with higher service charges may also require more cash to be kept aside.
The timing of planned improvements should be considered just as carefully, as refurbishment may support a higher rent but should not leave the portfolio without enough working capital.
Factor in tax
Tax can have a significant effect on the amount of cash a landlord ultimately retains, particularly because mortgage interest is not deducted in full when taxable rental profit is calculated for individual landlords. This can leave higher-rate taxpayers with larger mortgage balances paying tax on a figure that is higher than the cash profit they have actually received.
A qualified tax adviser can explain how the ownership structure affects the landlord’s position, which should be considered alongside the mortgage strategy to build a more realistic picture of the income retained.
Section 24 is the single biggest reason cash profit and taxable profit have drifted apart for individual landlords. Since April 2020, finance costs can no longer be deducted from rental income; instead landlords receive only a flat 20% tax credit, so a higher-rate taxpayer effectively pays around £200 more tax for every £1,000 of mortgage interest than under the old rules. The response across the sector has been a clear shift towards limited company ownership, which sits outside Section 24 and can still offset mortgage interest in full: Hamptons analysis of Companies House data shows more than 400,000 buy-to-let companies were in existence by early 2025, up from around 200,000 in mid-2020. Incorporation is not automatically the right answer, because stamp duty and capital gains tax can arise on transfer, and with Making Tax Digital for Income Tax now being phased in from April 2026 the compliance burden matters too. This is a decision to model carefully with a tax adviser alongside the wider remortgage strategy, not a default move.
Decide whether every property still earns its place
Refinancing is not always the best response to cash flow pressure, particularly where a property’s mortgage costs have risen or its rental performance has weakened. Higher maintenance requirements can also make a property less attractive to hold, in which case selling may release capital and reduce borrowing across the portfolio.
Any decision to sell should be based on the property’s longer-term position rather than a single difficult month, taking account of the costs involved and any tax that may be due. Equally, a property producing only a modest monthly return may still be worth keeping if it carries little debt or has strong future potential, so its role within the wider portfolio needs to be considered before a final decision is made.
Act before pressure becomes urgent
The best time to review portfolio cash flow is before a problem develops, using mortgage expiry dates and regular property reviews to spot where monthly costs may rise or performance is beginning to weaken. This gives landlords more time to consider the available options and reduces the likelihood of making a rushed decision. A mortgage adviser with experience in portfolio lending can review the current borrowing and assess whether it continues to support the landlord’s wider plans.
Encouragingly, the data suggests most portfolio landlords are managing these pressures by restructuring rather than retreating. Buy-to-let arrears eased again in the first quarter of 2026, with the number of loans more than 2.5% in arrears falling by 560 on the previous quarter, while the average gross rental yield held at 7.21% and outstanding BTL balances rose above £313 billion. Landlord confidence has held up too, with 93% of professional landlords surveyed expecting their portfolio value to rise in 2026.
In my experience, the landlords who navigate this environment best are those who treat portfolio review as a routine exercise tied to their mortgage expiry dates rather than a reaction to a single difficult month. Reviewing borrowing across the whole portfolio well ahead of time is what turns a potential cash flow problem into a manageable remortgage decision.
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FAQs
What is Section 24 of the Income Tax Act?
Section 24 is the rule, introduced from April 2020, that stops individual buy-to-let landlords deducting mortgage interest and other finance costs from rental income before tax. Instead, landlords receive a flat 20% tax credit on those finance costs, regardless of their income tax band. For a higher-rate taxpayer this means paying roughly £200 more tax for every £1,000 of mortgage interest than under the previous rules, which is why taxable profit and actual cash profit have drifted so far apart for many portfolio landlords. It is also the main reason so many landlords have looked at moving buy-to-let properties into a limited company, since companies sit outside Section 24 and can still offset mortgage interest in full.
How early should I start remortgaging a buy-to-let property?
As a general rule, start the remortgage conversation around six months before your fixed-rate deal ends. That lead time gives you room to compare lenders, test rental coverage against current interest coverage ratio (ICR) requirements, arrange any valuation work, and weigh a product transfer against a full remortgage. With so many buy-to-let deals maturing at once across the market, lenders and valuers are busy, so starting early for a buy-to-let remortgage reduces the risk of drifting onto a lender’s standard variable rate while you wait.
How do I manage rising buy-to-let mortgage payments?
Managing rising BTL mortgage payments starts with reviewing each property individually, comparing rent against mortgage costs and running expenses rather than looking only at the portfolio total. From there, model repayments at higher interest rates ahead of each mortgage expiry, check affordability against the lender’s interest coverage ratio, and look at borrowing across the whole portfolio rather than refinancing property by property. Keeping a dedicated cash reserve, planning improvements around cash flow rather than against it, and getting tax advice on how Section 24 affects your actual retained income all help absorb higher buy-to-let mortgage payments without relying on expensive short-term borrowing. If a property’s costs have risen faster than its rental performance, refinancing may not be the answer, and selling can sometimes do more to reduce pressure across the rest of the portfolio.
Is remortgaging a buy-to-let better than a product transfer?
Neither option is automatically better; the right route depends on what you need the mortgage to achieve. A product transfer, staying with your current lender, is usually the more straightforward choice and often comes with lower fees, but it may limit how much you can restructure the borrowing. A full buy-to-let remortgage with a new lender takes more time and paperwork but can open up a more competitive rate or allow you to release equity or adjust the loan structure. Landlords with several fixed-rate deals ending close together often benefit most from comparing both routes property by property, and property by property across the whole portfolio, well before any deal is due to expire.
