Borrowing more than they expected — nearly £190,000 more — was specific to their circumstances and not a typical result. But the principle holds: the calculator had no idea how to read one of them.

That gap is not unusual. It happens in the other direction too. I have sat with people who believed they could borrow considerably more than any lender would realistically offer, because no calculator had flagged the car finance deal they had forgotten about, or the credit card they rarely use but have never closed. The number on the screen is, at best, a rough orientation. It is not a mortgage offer, and it is not advice.

Here is what actually determines what you can borrow.

Income is more complicated than a salary

Most lenders work to an income multiple — traditionally somewhere between four and four-and-a-half times your annual income, with some prepared to lend at higher multiples depending on their specific criteria, the borrower's profile, and the loan-to-value ratio involved. That is broadly where calculators live. They take a number, they multiply it, they show you the result.

The problem is that income is rarely just a number.

If you are employed and paid a straightforward salary, lenders can usually assess you with confidence. They want to see payslips and your P60, and the picture is relatively clean. But a meaningful proportion of working people do not fit that template — and many do not realise quite how differently lenders interpret their earnings.

Take self-employed borrowers. If you run a limited company, some lenders will look at your salary plus dividends. Others will look at your share of net profit. Others will want a three-year average; some will accept two. The difference between those approaches can be enormous. A company director who takes a modest salary and leaves profit retained in the business may look far wealthier to one lender than another, depending entirely on methodology.

Contractors are assessed differently again — some lenders will annualise your day rate rather than rely on a salary figure, though how favourably this works in practice varies significantly by lender and contract type. Freelancers, partners in a firm, those with rental income, those with bonus structures, those returning from parental leave — each carries its own interpretation depending on who is doing the underwriting.

This is why lender selection matters as much as the lending multiple. It is not just about who will go highest; it is about who will actually read your income correctly in the first place.

What sits between your income and your mortgage

Even if your income is assessed generously, lenders do not simply look at what you earn. They look at what is left after your existing commitments — a calculation called affordability assessment, which has been central to responsible lending rules in the UK since the Mortgage Market Review of 2014.

Every financial commitment you carry reduces what you can borrow. A car loan. A student loan repayment. A credit card with a high limit, even if you clear it monthly. A buy now, pay later agreement. Maintenance payments. Some of these you might consider negligible; a lender's affordability model will not.

Stress testing sits on top of this. Lenders are required to check that you could still afford your repayments if interest rates rose materially. This is not a formality — it has a real effect on the ceiling a lender will set.

None of this appears in an online calculator. A calculator asks for your income and perhaps your existing debts, but it does not know which commitments your chosen lender will weight most heavily. It does not know whether you applied for a credit card eighteen months ago and were declined, or whether you have a mobile phone contract that appears on your file differently than expected. It is working without the file in front of it.

Before approaching a lender, there are a few practical steps worth taking. First, pull a copy of your credit report — services such as Experian, Equifax, or TransUnion allow you to do this for free, and checking for errors or surprises before a lender sees your file is always time well spent. Second, consider closing credit cards you no longer use; an open card with a high limit can affect your assessed affordability even if the balance is zero. Third, if you have any buy now, pay later agreements, make sure they are settled and accounted for — these appear on credit files and lenders treat them as active commitments.

I should say clearly here: your home may be repossessed if you do not keep up repayments on your mortgage. Borrowing the maximum a lender will offer is not always the right decision, and what you can borrow is a different question from what you should borrow.

Why lender selection is genuinely part of the answer

There are over a hundred active mortgage lenders in the UK. Roughly twenty of them are household names. The rest are specialist, building society, or private lenders who have different risk appetites, different underwriting teams, and different criteria for different borrowers.

Some lenders are highly competitive for straightforward employed borrowers with large deposits. They would struggle to assess a self-employed architect with three income streams and a retained profit position. Other lenders are specifically structured to handle exactly that. Neither is better in the abstract; the question is which one is suited to you.

This is not esoteric. It is the practical work of understanding what your income looks like on paper — not in your bank account, but in the eyes of an underwriter who has never met you and is reading a set of documents according to a criteria sheet. Getting that match right is often the difference between a disappointing decision in principle and one that reflects your actual financial position.

The borrowing figure that matters is not the one the calculator shows you. It is the one that emerges after someone has properly read your income, understood your commitments, and placed your application with the lender most likely to see your position clearly.

That is not a calculation. It is a considered process — and it is worth doing properly before you fall in love with a property.

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Lawes Financial is an independent mortgage broker (FRN 1046161), an appointed representative of Andrew Charles Consulting Ltd, which is authorised and regulated by the FCA. We work with over a hundred lenders across the market and specialise in cases where income is anything other than straightforward. If you would like to understand what you could realistically borrow — based on your actual circumstances, not a calculator — [book a consultation with our team](#). There is no obligation, and the conversation is always confidential.

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*Figures quoted are illustrative only. Your actual outcome will depend on your
individual circumstances, loan size, term, and the products available to you.*

*This is not financial advice. Speak to an independent mortgage broker before
making any decisions.*

*Lawes Financial Limited (FRN 1046161) is an appointed representative of Andrew Charles Consulting Ltd, which is authorised and regulated by the Financial Conduct Authority (FRN 304904).*