A credit score is a guess dressed up as a number

A credit score compresses years of financial behaviour into three digits and calls it an answer. It isn't. It is an estimate, built from how you have borrowed in the past and it says surprisingly little about whether you can afford what you are borrowing now.

Two customers can share the same score for completely different reasons. One pays off a credit card in full every month and has barely used any credit at all; the other has missed payments here and there but always caught up before it hurt the file. The number treats them the same.

A lender relying on the score alone is not getting a clearer picture, just an independent score to shield them from any underwriting mistake. It's what we call CYA.

What a credit score actually measures

Your score is built from your credit history, including whether you have repaid loans and credit cards on time, how much of your available credit you are using, how long your accounts have been open, how many recent applications you have made and any defaults or CCJs on record. That is valuable information, it is just not the whole picture and, more importantly, it is not current information. What might have been a CCJ four or five years ago still affects your score, and likely unfairly so given the passage of time.

What a credit score does and doesn't measure

Two things carry most of the weight in that number: payment history (whether you have paid what you owe, on time) and credit utilisation (how much of your available credit you are using at any given moment). Account age, the number of recent applications and any defaults or CCJs on the public record sit behind those two. It is a narrow, backward-looking measure of borrowing behaviour, and within that narrow lane it does its job reasonably well.

What the score measures:

• Payment history on existing credit and loan accounts
• Utilisation: how much of your available credit limit is in use
• Length and age of your credit accounts
• Number of recent applications and hard searches
• Defaults, CCJs and other public record entries

What it never measures:

• Whether your income lands consistently or fluctuates month to month
• Whether your spending sits comfortably within that income
• How much is left over after rent, bills and existing commitments
• Whether you are building savings or relying on an overdraft to get by

None of that second list shows up in a credit file, because a credit score was never built to answer it; it answers a narrower question about repayment behaviour, and a mortgage decision needs an answer to a bigger one, which is whether a customer can afford the payment given what happens in their bank account each month. This is the same gap that leaves thin credit file customers looking riskier than they are: there is not enough borrowing history for the score to work with, whatever the reality behind it.

That gap between the two lists is exactly what the rest of this comes down to: a score built to describe the past, set against data built to describe the present.

What open banking adds

Open banking replaces the estimate with real income, real spending and real savings, direct from a bank account. Instead of inferring affordability from how a customer has handled debt in the past, a lender can see the money moving in and out right now. That is a much better test of whether a mortgage is affordable and it is not just a test of whether a customer has historically repaid what they borrowed.

Where the score falls short

Consider a young professional who has always rented and paid in cash, a self-employed contractor with variable monthly income or a customer recovering from a difficult period after redundancy or illness. A credit score can make all three look riskier than they are, because it has no way to see the steady income or the controlled spending sitting underneath.

Better together, not either or

This does not make the credit score irrelevant. Missed payments and defaults matter and always will. What changes is the weight given to a single number when the fuller picture is available to see. A customer with a modest score but two years of stable income is a different risk to a customer with the same score and three months of overdraft use. The score alone cannot tell those two customers apart, the bank transaction data can.

Same score, different mortgages: a worked example

Take two customers, both applying for a £280,000 mortgage, both earning £42,000 a year, both showing a credit score of 720 on the same reference agency scale. On the file alone, a lender has no reason to treat one differently to the other.

The first customer keeps two credit cards, clears them in full every month and has held a current account for eight years with a car loan paid off without a late payment. Card utilisation is low, the history is long and the score reflects it fairly.

Underneath, the account tells a different story. Spending runs close to income most months, an overdraft of £600 gets used four or five times a year to bridge the gap and there is no consistent saving pattern.

The second customer has a thinner file: one credit card, opened three years ago, carrying a modest balance paid down steadily. A missed payment from early in that history has already dropped off the record. The score lands in the same place but for different reasons.

Underneath, the account shows something the first file cannot. Income lands on the same date every month, spending that leaves £400 or more spare and that amount going into savings without fail.

A lender working from the score alone sees two identical risks. A lender working from open banking sees two different affordability cases, one customer with less room to absorb a mortgage payment on top of existing spending and one with a built in buffer already in place. A broker comparing the two case files would reach a different recommendation for each, even though the credit file alone would treat them the same.

What you can do right now

• Check your credit file with the credit reference agencies so you know what a lender already sees.
• Review three to six months of your own bank statements before you apply; a lender using open banking will see exactly what you would see.
• Ask your broker or lender whether they use open banking alongside the credit check; increasingly, the better ones do.
• If your score and your bank data seem to disagree, ask a broker to help present the fuller case rather than leaving the number to speak for itself.

A number built from the past is a reasonable starting point. It is not the whole story, and it should not be treated as one.

Find out where you stand — before you apply. Check my readiness →

Frequently asked questions

Does open banking replace my credit score?

No. A credit check still happens on every mortgage application. Open banking works alongside it, letting a lender see real income and spending data that a credit file was never built to capture. The two work together, not one instead of the other.

Will checking my mortgage readiness affect my credit score?

No. A mortgage readiness check uses a soft credit search alongside open banking data and a soft search leaves no mark on your file and is not visible to other lenders or brokers.

Can I have a good credit score and still struggle to get a mortgage?

Yes. A high score reflects tidy repayment behaviour. It says nothing about whether your income comfortably covers a mortgage payment on top of everything else you spend each month. A lender who looks past the score to the bank data can catch affordability gaps a good score hides, in both directions.

What do lenders see that a credit score doesn't show?

Real income landing in your account, real spending patterns, how much is left over after essential costs and whether you are building savings or relying on an overdraft. None of that sits in a credit file.

Is a lower credit score always a problem for a mortgage application?

Not on its own. A modest score backed by stable income and controlled spending is a different case to the same score backed by irregular income and frequent overdraft use. A broker who understands that distinction can present the stronger of those two cases properly, rather than letting the number speak for itself.

How much weight do lenders give a credit score compared to open banking data?

It varies by lender and by broker recommendation. Most still start with a credit check to rule out anything adverse, then use open banking data to build the actual affordability picture behind the number. Expect that balance to keep shifting toward open banking as more lenders adopt it.

Do all lenders and brokers use open banking alongside a credit check?

Not yet universally, though adoption keeps growing. It is worth asking a lender or broker directly whether open banking data forms part of their affordability assessment before you commit time to an application.

Does a joint mortgage application change how credit scores are used?

Yes, in that a lender weighs both borrowers' files and both sets of account behaviour together, not just one score in isolation. A weaker score on one side does not automatically drag down a joint application that has a strong combined affordability case behind it.

What can I do if my credit score doesn't reflect my real financial position?

Start by checking your own bank statements the way a lender would, over three to six months, then talk to a broker about lenders that give weight to that fuller picture rather than the score alone. Checking your mortgage readiness before you apply shows you that same picture in advance.

Why do two customers with the same credit score sometimes get different mortgage offers?

Because the score is built from repayment history alone, and a lender using open banking data can see the affordability picture behind it including income, spending and saving behaviour that two customers with an identical score can differ on completely. That difference, not the score, is often what decides the offer a lender or broker can put forward.