McGrath: Red Hat’s commitment to open source

The bank does not physically check the signatures. The organisation setting up the direct debit asserts to the bank that they have received appropriate permission (a signature isn't the only way). In exchange, the end-user gets prior notification of the direct debit and can cancel it anytime and even undo any direct debits for the last 13 months. And the bank will charge the organisation setting up the DD a hefty charge-back fee. Do it too often and they'll kick you off altogether.

For this reason my apartment management refuses to do DD for the monthly service costs, because of shenanigans with people selling their apartment and then reversing all the fees for the previous year. Sure, you can prove that you had the right to do DD, even a signature, but you'll have to send it to debt collection or even the courts to get your money.

So yes, someone could publish their IBAN here and I could (attempt to) setup a direct debit for it, but it would be fraud. Really big organisations like energy and insurance companies use DD because people undoing direct debits without cause is just another one of the many things that can go wrong and it's just a cost of doing business.