A credit score is a summary produced by a model. Lenders see the file the model was built from, and they apply criteria of their own that the number never reflects.
The score is one input among several
Lenders combine the bureau data with information from the application, their own records of the customer and their current appetite for risk.
A score that appears strong can still fail a lender's policy, and a modest score can be approved where other evidence is favourable.
This is why identical applicants receive different answers from different lenders on the same day.
Consumer-facing scores add a further complication, since they are often produced by a different model from the one a lender uses. The number seen and the number applied are rarely the same.
Affordability is assessed separately
Credit history describes how obligations have been handled. It says little about whether a new commitment fits alongside current income and outgoings.
Lenders therefore assess affordability using declared income, verified where required, and existing commitments visible on the file or disclosed in the application.
An applicant with an excellent history can be declined purely on affordability, which is a common and often confusing outcome.
The detail behind the summary matters
The file records when accounts opened, how balances moved, when payments were late and by how much. A score compresses all of that into a single figure.
A lender reading the detail can distinguish a single administrative late payment years ago from a recent pattern of arrears, even where both affect the score similarly.
Recent behaviour generally carries more weight in that reading than older entries, regardless of what the number suggests.
Different bureaus hold different data
Not every lender reports to every bureau, so files held by different agencies can differ in content and therefore produce different scores for the same person.
A lender using one bureau sees only what that bureau holds, which is why checking a single score gives an incomplete view of what applications will encounter.
Errors also occur in one file and not another, and correcting one does not correct the rest.
Internal data is invisible from outside
An existing customer's behaviour with that institution, including account conduct and overdraft use, is available to it and to nobody else.
This can work in either direction, and it explains approvals or declines that appear inconsistent with the external file.
Because criteria are commercial and unpublished, no score can predict a specific lender's decision. It indicates a general position rather than an outcome.