A credit score is widely treated as a report card on financial virtue. It is not. It is a
prediction, generated by a model, of how likely you are to fall behind on a payment in the near
future. Understanding that distinction explains most of the behaviour that otherwise seems
arbitrary.
Payment history and utilisation do most of the work
Whether you have paid on time, and how much of your available credit you are using, together
account for the bulk of most scoring models. Payment history is the single largest factor, which
is why one missed payment can move a score more than months of careful management.
Utilisation is the more controllable of the two. It compares balances against limits, and it
is measured at the moment the lender reports — not at the end of the month. Someone who clears
their balance in full every month can still show high utilisation if the report happens to land
before the payment does. Paying before the statement date, rather than before the due date,
fixes that at no cost.
Age, mix and applications
The remaining factors are less intuitive. Length of credit history rewards accounts that have
been open a long time, which is the main argument against closing an old card simply because it
is unused. Credit mix gives modest credit for managing different types of borrowing. Recent
applications leave a temporary mark, so several applications in a short window will depress a
score briefly.
None of these is worth engineering around. A score responds to consistent, unexciting
behaviour over time, and attempts to optimise it with clever manoeuvres generally produce less
than simply paying on time and keeping balances low.
