Checking details by account number sounds like the natural thing to do and is close to the least informative check available. The account number is the one field in the set that carries no independent meaning: it identifies an account inside an institution and tells you nothing without knowing which institution. Everything useful in a check comes from the other fields.
Why the account number alone tests almost nothing
The arithmetic that makes UK account numbers testable is indexed by sort code range, so without the sort code there is no rule to apply. An account number with no sort code can be tested for length and nothing else. There is also no register of account numbers anywhere, licensed or public, so there is no lookup that could take a bare account number and return anything at all about the account behind it.
What the full set can establish
With the sort code, the account number and the name, three things become possible. The modulus arithmetic tests whether the number is consistent with the institution. The sort code can be matched against what the institution publishes about itself. And the name check asks the receiving bank whether the name matches, which is the only one of the three that involves the other institution at all. Anything that matters comes from the third.
Checking details somebody sent you
Treat the channel as the risk rather than the digits. Details that arrive in an email or a message, especially details that replace ones you already have, are the shape of almost every serious payment fraud. Telephone the payee on a number you held before the message arrived. Add the payee in your banking app so the name check runs. Send a small first payment where the relationship is new. Those three steps are worth more than any amount of digit checking.
Checking your own before you give them out
Read them from your bank's app rather than from memory or an old document, because a migrated product can carry different details. Include the account name exactly as the account is held, which is the field that causes most avoidable delays on business payments. If you are giving details for an incoming international payment, give the IBAN and the BIC as well, both of which your bank publishes, and label each field so the payer is not guessing from lengths.
Questions people ask about check bank account details
Can I check bank account details by account number alone?
No. Without the sort code there is no rule to test the number against, and no register maps an account number to anything.
What is the most useful check on a set of details?
The name check that runs when you add a payee, because it is the only one that asks the receiving bank anything.
Should I check details that a supplier emailed me?
Confirm them by telephone on a number you held before the email. Digit checks will pass on a fraudster's real account.
Do I need to check details for an incoming payment?
Check what you give out, not what you receive. Read your own details from your bank's app and label each field for the payer.