Account number verification.

Best to ask this in uk.people.consumers.ebay

I believe the reason eBay ask for this information is to set up a direct debit for the seller to pay his charges from. If you give incorrect information then direct debit would fail and they'd be back to you asking for payment by some other method.

Chris

the last of which allows entry of sort code & a/c number, so presumably ebay can do the same sort of thing?

I did a quick check on the Validation and it came back with the correct results when I entered true details and false details

Allan

In message , Allan Gould writes

How could you be SURE they were false details? In other words, you could input details that weren't your which could have been valid for somebody else.

"john boyle" wrote

Perhaps an old account of his which he's now closed?

In message , Tim writes

AIUI, it doesnt validate the existence of an account ar attribute a particular sort code and account number to an individual, just that the account number is a member of the set of valid account numbers that could exist.

(This is just my theory and I am quite willing for to be disproved).!!

We use software like this:

I don't know, I've tried putting my own account number with one digit wrong and it tells me it's invalid, presumably that would be within a range of account numbers? I thought the site might be using the Luhn 10 formula, my sort code together with my account number at one bank does match the Luhn 10 formula as its part of my switch card number. I thought by entering a false account number that matches Luhn 10 it would say it was valid but it doesn't. Unless theres some formula or method I don't know about, I think the site must have some real time way of checking if an account number is valid or not.

They use a modulus 10 or modulus 11 check. A 6 digit number (for example 113558) is made into a 7 digit number by inserting one additional "check" digit, usually at the end or beginning. The check digit is calculated by applying a formula (or using a table) to each of the original 6 digits, one at a time, resulting in 6 new (temporary) numbers. The temporary numbers are (usually) added together and their sum is subtracted from the next highest multiple of

1. So, a sum of 57 would be subtracted from 60 and the check digit would be 3. The final account number would then become 1135583.

Modulus 10 checks give you a 90% chance of picking up a single keying error (including number reversal) so some still slip through. Modulus

Account number range and other checks are done by the Banks themselves but these would only be of use to outsiders if the Banks chose to publish the ranges, unused account numbers etc., which I don't think they do. Hope that helps.

I dot know what Luhn is but is it based on a modulus check? In any event you are checking a card number, which is not the same as an account number check because cards carry more digits than the basic sort code & account number (6+8).

Bank account numbers are made up of 8 digits (although one well known bank suppresses a digit) the first few of which are used as various identifiers by the bank, e.g. if the 3rd digit was a 9 for one very well known high street bank this meant it was a staff members account.

The whole account number had to satisfy a modulus check so that, in the old days, when the account numbers were being input by a clerk on a mechanical punched tape machine, the machine could spot an account number as being not a member of the set of feasible account numbers. Different branches had different moduli. Also, the first digit was a 'balancing' number, but dot ask me how this worked. All of this meant that account numbers weren't sequential, there would be irregular gaps in the run of numbers. So, in summary, and having done some more research since my original post, AFAICS, those online sites DONT perform an account specific check, just a 'is it possible' type check.