Especially in the UK, bank sort codes are typically presented to the user as e.g. 04-00-04 by every banking app or website, but whenever you have to enter them (e.g. to pay someone else) they usually require you to not enter the dashes. Some of the most annoying sites limit the input to 6 characters but don't strip out the dashes, so you'd end up with 04-00- and then it complains.

And then there are the ones that implement it as 6 separate boxes, and these are the only fields in the form that auto advance to the next field on input and also often break delete if you want to undo the previous digit.