The most popular way to transfer money between friends in Poland is a BLIK-to-phone-number transfer. Those transfers are done from the banking app. I don’t need to know someone’s account number, I just need their phone number. BLIK transfers are instant, unlike regular bank transfers, which may take up to 1 business day (specifically, they are done via batch processing 3 times in a business day), and they are always free, unlike instant bank transfers (though that depends on your bank/account type).