9 Things That Reduce How Much You Can Borrow on a Mortgage
Mortgage affordability isn’t just about your salary. Lenders look at your income against your regular monthly commitments, and a handful of everyday costs can quietly bring the borrowing figure down, sometimes by more than people expect.
Here are nine of the most common things that reduce how much you can borrow on a UK mortgage, and what actually happens when a lender sees them on your bank statements or credit file.
1. Klarna and Buy Now, Pay Later
Klarna and other Buy Now, Pay Later (BNPL) services reduce how much you can borrow by lowering your disposable income during affordability checks.
Lenders look at your regular monthly commitments. Active BNPL instalment plans count as regular commitments, which reduces the leftover income you have available to pay a mortgage. The more you owe on BNPL when you apply, the lower the maximum loan a lender will offer.
There are a couple of other effects worth being aware of:
- Frequent or habitual use of short-term credit can flag potential cash flow issues. Lenders may question your financial habits or lower the borrowing figure as a precaution.
- Missed or late BNPL payments show up on your credit report and can cause a lender to reduce their offer, or reject the application entirely.
The simplest fix is to clear active BNPL balances well before you apply and avoid opening new plans in the months leading up to the application.
2. Undeclared bonuses
Undeclared bonuses reduce your maximum borrowing because lenders base their affordability calculations on verified, predictable income. If a bonus isn’t declared or evidenced, the lender treats your basic salary as your total earning power.
Most mainstream lenders calculate your borrowing cap using a standard income multiple, usually around 4 to 4.5 times your base salary, sometimes higher for particular professions or higher earners. A cash or performance incentive that doesn’t appear on payslips, your P60 or your tax return remains invisible to the underwriter, so it never feeds into the loan-to-income calculation.
Regular, evidenced bonuses can usually be included. Some lenders count them at 100%, others at 50% or 75%. It’s worth making sure your broker has full visibility of anything that could stretch the number, it can meaningfully change the affordability position.
3. Car finance
Car finance reduces your borrowing capacity because your monthly car payment counts as a fixed outgoing on the affordability assessment.
Lenders take your income, subtract your regular commitments, and use what’s left to work out what you can afford as a mortgage payment. A monthly car payment sits squarely in that commitments column. As a rough guide, every £200 a month of car finance can reduce your total mortgage borrowing by tens of thousands of pounds, the exact figure depends on the lender’s income multiplier and their affordability model.
If you’re close to a mortgage application, it’s worth thinking carefully about how car finance affects your position, clearing it, delaying a new agreement, or accepting a slightly lower borrowing figure might all be the right call depending on your situation. A broker can help you weigh the trade-offs, especially since paying off large debts right before an application can also reduce your cash reserves.
4. Childcare costs
Childcare costs reduce your borrowing power by lowering your available monthly disposable income. Lenders treat nursery fees, childminders and regular after-school clubs as essential financial commitments, similar to a loan or car finance.
Every lender uses a slightly different affordability model, so the reduction in borrowing power varies from one lender to another. Some are more flexible than others, particularly when future changes to childcare costs are on the horizon.
A few points that can help:
- Some lenders account for the age of your children and will recognise when childcare costs will drop, for example, once a child starts school.
- Formal evidence of change, such as a school acceptance letter, allows some lenders to factor in lower future costs.
- Government schemes like Tax-Free Childcare and funded hours are usually accounted for. Lenders base their calculations on the net cost after these are applied.
Because the treatment varies so much, this is one of the areas where broker knowledge of individual lender criteria can genuinely change the borrowing figure.
5. Student loans
Student loans reduce how much you can borrow because lenders treat the monthly repayment as committed expenditure, the same way they treat car finance or childcare.
Two useful things to understand:
- The balance is irrelevant. Lenders only look at how much is coming out of your bank account each month, not how much you owe overall.
- Student loans don’t appear on your credit report. They’re collected through PAYE and don’t affect your credit score, so they can’t trigger a credit-based rejection. The only impact is the monthly repayment showing up in your affordability calculation.
6. Regular transactions to family or friends
Regular payments to family or friends can affect your affordability depending on how they’re treated.
If you’ve taken a formal loan from a family member, some lenders may reduce your borrowing figure, or, in some cases, decline the application, if they consider your total debt too high relative to your earnings. If the money from family was a genuine gift with no repayment expected, it doesn’t create a monthly outgoing and doesn’t affect the calculation.
The grey area is regular transfers that show up on your bank statements without clear context. If a lender sees consistent monthly payments going to a family member, they may ask whether it’s a loan, rent, or something else, and how they treat it depends on your explanation and any supporting evidence.
7. JBSP mortgages
Being a joint borrower on a JBSP (joint borrower sole proprietor) mortgage reduces how much you can borrow for your own separate mortgage, because lenders treat the full JBSP debt as your financial commitment.
Even though you don’t own the property, the lender views the entire JBSP loan as your debt. When you apply for a new mortgage of your own, the lender factors in your legal responsibility for the JBSP monthly payments, which lowers the maximum they’ll lend you.
Two additional points:
- The monthly commitment counts against your disposable income in the standard affordability check.
- Any missed or late payments on the JBSP mortgage affect your credit history, which can further lower your borrowing or lead to a rejection on your own mortgage.
8. High travel and commuting costs
High travel and commuting costs can reduce your borrowing capacity because lenders subtract essential monthly outgoings from your income to calculate true disposable income. Every pound spent on regular travel is a pound less available to service a mortgage payment.
A few specifics worth knowing:
- Underwriters review your bank statements for consistency between your declared travel costs and your visible outgoings on fuel, rail tickets or public transport.
- Travel funded via credit cards or car finance can be a double hit, because the underlying debt commitment shows up too.
If you don’t provide custom figures, many lenders apply default statistical models based on household size and geographic location. These defaults aren’t always accurate for your specific situation, but they still feed into the calculation.
9. High household bills
High household bills lower your available disposable income, which reduces what a lender will let you borrow.
Utilities, council tax, broadband and other regular household commitments all count as monthly outgoings when a lender works out your affordability. The higher your fixed household costs, the less headroom the lender has to lend against.
As with travel, if you don’t provide your actual figures, lenders will often apply statistical averages based on household size and location, which may or may not reflect what your bills actually look like.
Talk to Heron Financial
Mortgage affordability is often less about the number on your payslip and more about what’s happening across your bank statements. If you’re not sure how your specific commitments would affect what a lender will offer, we can walk through your position, look at where the strongest lender fit is likely to be, and work out whether there’s anything worth adjusting before you apply.
This article is general information, not personal financial advice.
FAQs
How far back do mortgage lenders look at bank statements?
Most lenders ask for three months of bank statements, though some request six. They're looking for regular commitments, any unusual transactions, and signs of financial stress like frequent overdraft use or gambling activity.
Should I clear my debts before applying for a mortgage?
Sometimes. Clearing high-interest revolving debt like credit cards or BNPL is usually helpful. Paying off large debts like car finance or a personal loan very close to an application can hurt as much as help, because it eats into your deposit and cash reserves. It's worth running through the options with a broker before making the call.
Do overdrafts affect a mortgage application?
Yes. Being in your overdraft regularly can suggest you're not living within your means, which lenders take seriously. Occasional use is much less of an issue.
Do gambling transactions on my bank statements affect my mortgage?
They can. Regular gambling transactions, particularly if the amounts are significant relative to your income, can concern lenders and affect their willingness to lend. Occasional small transactions are usually not a problem.
How much can I borrow on a UK mortgage?
Most lenders use an income multiple of around 4 to 4.5 times your base income as a starting point. Some professionals and higher earners can access higher multiples. The exact figure depends on your income, your commitments, your deposit and the lender's specific criteria.
Do I have to declare all my expenses on a mortgage application?
You'll need to declare your regular commitments, loans, credit cards, childcare, student loans and so on, accurately. Failing to declare something that shows up on your bank statements can lead to a rejection or an offer being withdrawn later in the process.