Direct debits as a seller: You file the direct debit with your bank. This can normally be done online through a web interface or various APIs (e.g. HBCI). The transaction is then processed through the Eurozone's TARGET2 system, i.e. the amount is withdrawn from the buyer's bank account and credited to the seller's bank account. This works in the entire Eurozone and is supposed to not take longer than a day. In practice, some countries take longer. E.g. I've seen payments between Germany and Italy take 3 days, but between Germany and France or within Germany it always takes 1 day.