Same Salary, Different Mortgage Amounts: Why Your Income Alone Does Not Tell the Full Story
One of the most common assumptions people make when they start thinking about buying a home is this:
“If I earn X, I should be able to borrow Y.”
Usually, that expectation comes from the well known “4.5x income” rule. You multiply your salary by 4.5 and assume that is roughly what a lender will offer you.
For some people, that estimate turns out to be fairly accurate. For many others, it does not.
Two people can earn the same salary and be offered very different mortgage amounts. This often comes as a shock, especially when you feel like you are doing “everything right”. It can also feel unfair, confusing, or personal.
In reality, this difference is completely normal. Mortgage lending is not just about income. It is about affordability, income structure, and how your real life finances fit together.
This article explains why the same salary does not always lead to the same borrowing power, what lenders actually look at, and how understanding this early can save you a lot of stress later on.
The 4.5x Income Rule: Where It Comes From and Why It Misleads People
The 4.5x income multiple exists because it is simple. It gives people a rough starting point when they begin thinking about buying a home.
If you earn £40,000, multiplying that by 4.5 suggests a mortgage of around £180,000. Many online calculators are built around this idea, and it is often mentioned in conversations with friends, family, or colleagues.
The problem is that this figure is not a promise. It is not a universal rule. And it is certainly not how lenders make their final decisions.
Some lenders can go higher than 4.5x income in certain circumstances. Others will not go anywhere near it. The multiple itself is only one small part of a much bigger affordability assessment.
Relying too heavily on this figure can lead people to look at properties that are not realistic for their situation, or to feel discouraged when the numbers they are offered do not match their expectations.
Why Lenders Do Not Just Lend Against Salary
Mortgage lenders are not lending based on what you earn. They are lending based on whether you can comfortably afford the repayments over the long term.
This is an important distinction.
Income tells a lender how much money comes in. Affordability tells them how much flexibility you have once everything else in your life is taken into account.
That means lenders look closely at what goes out of your account every month, not just what comes in.
They want to understand whether you could still manage your mortgage payments if interest rates increased, if your circumstances changed, or if unexpected costs came up.
This is why two people earning the same salary can end up with very different borrowing limits.
Affordability: The Part Most Buyers Underestimate
Affordability is where the biggest differences appear.
When a lender assesses affordability, they look at a range of outgoings and commitments, including:
Credit cards, even if you rarely use them
Personal loans
Car finance or leasing agreements
Childcare costs
Maintenance payments
Dependants
Regular spending commitments
Even if you are managing these costs comfortably right now, they still reduce the amount a lender believes you can safely borrow.
For example, two people earning £40,000 might look identical on paper at first glance. But if one has no debts and low monthly outgoings, and the other has car finance, credit cards, and higher fixed costs, their affordability will look very different to a lender.
This is not a judgement on how you live your life. It is simply how lenders assess risk.
Not All Income Is Treated the Same
Another major reason borrowing amounts can differ is how income is made up.
Many people assume that if their total earnings are the same, lenders will treat them the same way. That is not always true.
Basic salary is usually the most straightforward form of income. Most lenders will use 100 percent of basic salary when assessing affordability.
Variable income is different. This includes things like:
Bonuses
Commission
Overtime
Shift allowances
Some lenders will include variable income, but often only partially. Others may require a history of that income over a certain period, such as 12 or 24 months. Some lenders will average it. Others may ignore it altogether.
This means two people earning the same overall amount, but with different income structures, can be assessed very differently.
For example, someone earning £40,000 as a fixed salary may be treated more favourably than someone earning £30,000 basic plus £10,000 in commission, even though the total income is the same.
Understanding how your income is viewed by different lenders can make a significant difference to what is possible.
Why Some Lenders Can Go Higher Than 4.5x Income
You may have heard that some lenders can offer mortgages closer to 6x or even 7x income in certain cases.
This is true, but it comes with conditions.
Higher income multiples are usually reserved for borrowers with:
Strong affordability
Low outgoings
Stable and predictable income
Good credit history
They are also more common at higher income levels, where lenders assume there is more flexibility in spending.
Even then, not every lender offers higher multiples, and not every borrower will qualify. This is why two people on the same salary can receive very different answers depending on which lender they approach.
It is also why relying on a single bank or online calculator can give a misleading picture of what is available to you.
The Difference Between “Can Borrow” and “Should Borrow”
Another important distinction that often gets overlooked is the difference between what you can borrow and what you should borrow.
A lender may be willing to offer you a certain amount, but that does not automatically mean it is the right choice for your life.
Some people are comfortable stretching themselves financially. Others value flexibility, savings, and peace of mind. Neither approach is right or wrong, but they lead to very different decisions.
Understanding your borrowing power early allows you to make choices that align with how you actually want to live, not just what a lender is prepared to offer.
Why Online Calculators Often Fall Short
Online mortgage calculators can be useful as a starting point, but they rarely tell the full story.
Most calculators rely on broad assumptions and do not take into account the detail of your personal circumstances. They often assume a standard income structure, average outgoings, and a generic lending approach.
This can lead to false confidence or unnecessary disappointment.
A proper affordability assessment looks at your real figures, your actual commitments, and how different lenders interpret them.
How This Impacts First Time Buyers in Particular
First time buyers often feel this disconnect most strongly.
Many have spent years saving a deposit, watching the market, and mentally planning their purchase around a number they believe they should be able to borrow.
When reality does not match that expectation, it can feel like a setback or a failure.
In truth, it is simply part of the process.
Getting clarity early on what is realistic for you allows you to focus your energy on homes that genuinely fit your situation, rather than chasing a number that was never guaranteed in the first place.
Why Getting Clarity Early Changes Everything
Understanding how lenders see your income and affordability before you start house hunting can completely change your experience.
It helps you:
Avoid falling in love with homes that are not realistic
Make confident decisions rather than reactive ones
Feel in control of the process
Plan next steps with clarity
It also gives you time to adjust if needed. That might mean paying down certain debts, reviewing spending, or simply choosing a different timeline that suits you better.
None of this needs to be rushed. And none of it means you are behind.
Final Thoughts
The idea that salary alone determines your mortgage borrowing power is one of the biggest misconceptions in home buying.
Two people on the same income can and often do receive very different mortgage offers. This is not a reflection of success, failure, or worth. It is simply how lending works.
Mortgage decisions are shaped by affordability, income structure, commitments, and how different lenders assess risk.
Understanding this early allows you to approach buying a home with clarity rather than assumption, and confidence rather than confusion.
If you are thinking about buying, or even just starting to explore the idea, getting clear on how your situation looks through a lender’s eyes is one of the most valuable steps you can take.
Your home may be repossessed if you do not keep up repayments on your mortgage or other loan secured against it.
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Because mortgage lending is based on affordability, not just income. Lenders look at your monthly commitments, outgoings, dependants, and how your income is structured. Two people earning the same amount can have very different financial commitments, which affects how much a lender is willing to offer.
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The 4.5x income figure is a general guideline, not a guarantee. Some lenders may offer less, while others can offer more in certain circumstances. The final amount you can borrow depends on affordability checks, your income type, and the lender’s individual criteria.
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They can, but not always in full. Many lenders treat variable income differently from basic salary. Some will only use a percentage of bonuses or commission, some will average them over time, and others may not include them at all. This is why income structure matters as much as the total amount you earn.
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The best way is to have a full affordability assessment based on your real income and outgoings, rather than relying on online calculators. This gives you a clearer, more accurate picture of what is realistic for you and helps avoid disappointment later in the process.
