How much can I borrow? A plain-English guide to mortgage affordability
Affordability is the question every first-time buyer asks first - and gets the most confusing answers to. In this post, we cut through the jargon and explain exactly how lenders decide what they will lend you, and what you can do to put yourself in the strongest possible position.
Why affordability feels so confusing
Ask five people how much they can borrow for a mortgage and you will get five different answers - usually based on a mixture of what a friend was told, a quick go on an online calculator, and what an estate agent said before you had even spoken to a lender. The reality is more nuanced than any of those sources suggest.
Mortgage affordability is not a single fixed figure. It is a calculation that every lender runs slightly differently, based on your income, your outgoings, your credit history, and the size of your deposit. Understanding how that calculation works puts you in a significantly stronger position - both when you start looking at properties, and when you sit down to make a formal application.
Income multiples: a starting point, not the whole story
Most lenders start with an income multiple - typically between 4 and 4.5 times your annual gross income, though some lenders will stretch to 5 or even 6 times in certain circumstances. For a single applicant earning £40,000, that represents a maximum borrowing range of approximately £160,000 to £180,000 at the standard multiple, or up to £240,000 at the higher end with a specialist lender.
For joint applications, lenders generally use the combined income of both applicants. Two applicants each earning £35,000 - a combined income of £70,000 - could therefore borrow in the region of £280,000 to £315,000 at a standard multiple.
However - and this is the crucial point - income multiples are a starting point, not a ceiling. What you can actually borrow is determined by a more detailed affordability assessment that looks at your full financial picture.
What lenders actually assess
Modern mortgage affordability assessments, introduced following the Mortgage Market Review of 2014, require lenders to stress-test your ability to repay the mortgage not just at the current interest rate, but at a higher rate - typically 3% above the product rate. This is designed to ensure you could still afford the mortgage if rates were to rise after you took it out. Very recently, the Financial Conduct Authority has allowed lenders to relax some of this stress testing, allowing more to be offered to borrowers.
Beyond income and stress-testing, lenders will examine:
• Committed expenditure - regular financial commitments including car finance, personal loans, student loan repayments, credit card minimum payments, and any other credit agreements. Each of these reduces the amount a lender is willing to advance.
• Household expenditure - lenders use statistical models (and increasingly, bank statement analysis) to assess your general living costs based on factors including the number of dependants in your household and the region you live in.
• Your deposit - a larger deposit means a lower loan-to-value ratio (LTV), which typically opens access to lower interest rates and, in some cases, more generous affordability assessments from lenders competing for lower-risk business.
• Employment status - employed applicants are generally assessed more straightforwardly than self-employed applicants, who typically need two years of accounts or tax returns to demonstrate their income history.
Your credit score and credit history
Your credit profile is one of the most important factors in a mortgage application - not just for determining whether you will be accepted, but for determining which lenders and rates are available to you. A strong credit history opens the full market; a history that includes missed payments, defaults, or County Court Judgements (CCJs) significantly narrows your options and typically increases the rates you will be offered.
Before you apply for a mortgage, it is worth checking your credit file through one of the three main credit reference agencies - Experian, Equifax, or TransUnion. All three offer free access through services such as Credit Karma, Clearscore, or their own apps. Check all three, as lenders may use different agencies and errors do occur. If you find any inaccuracies, raise a dispute to have them corrected before your application.
The mortgage in principle: your house-hunting starting point
A mortgage in principle (MIP) - sometimes called an agreement in principle or decision in principle - is a conditional indication from a lender of how much they would be willing to lend you, based on a basic assessment of your income and a credit check. It is not a guarantee, and it is not a full mortgage offer, but it serves two important practical purposes.
First, it tells you - with reasonable confidence - what budget you are working with when you start viewing properties. Second, most estate agents will ask to see evidence of a mortgage in principle before taking your offer seriously. Having one in place signals that you are a credible buyer, which matters in competitive markets.
A mortgage in principle can typically be arranged within a few hours through a broker, and is usually valid for between 60 and 90 days. If it expires before you have found a property, it can simply be renewed.
How to maximise what you can borrow
There are several things you can do - ideally in the months before you apply - to improve your affordability position:
• Avoid taking out new credit in the six months before applying. New credit applications leave marks on your credit file and reduce your available credit headroom.
• Register on the electoral roll at your current address, if you are not already. Lenders use electoral roll data as a basic identity and stability check.
• Save the largest deposit you can manage. Crossing LTV thresholds - particularly 90%, 85%, 80%, 75%, and 60% - opens access to progressively lower interest rates and broader lender choice.
• If you are self-employed, ensure your tax returns are filed and up to date. Two years of evidence is the standard requirement; three years is better.
A note from J Finance
Every borrower's situation is different, and the figure an online calculator gives you is almost never the same as what a lender will actually offer. J Finance provides a whole-of-market affordability assessment that compares the lending criteria of every lender available to us - not just one. If you are starting your house-hunting journey, or simply want to know where you stand before you begin, contact us for a no-obligation conversation. It takes less than an hour and gives you a clear, accurate starting point.