Too much validation

[pne]

I tried to transfer some money online just now.

However, the bank's form didn't like the copy-and-pasted account number, saying that "no special characters, spaces, or letters are allowed".

Why can't the field simply allow (and ignore) spaces? It's certainly wide enough.

Strangely enough, the bank sort code field happily accepted the number with spaces in the usual "123 456 78" form. (It didn't always; the field used to be limited to eight characters so if you copy-pasted a normally-formatted sort code, the last two characters got lopped off.)

I wonder what would be so bad about allowing spaces in the bank account number.