Depends on the country. In the UK the Direct Debit Guarantee states that "If an error is made in the payment of your Direct Debit, by the organisation or your b

Depends on the country. In the UK the Direct Debit Guarantee states that "If an error is made in the payment of your Direct Debit, by the organisation or your bank or building society, you are entitled to a full and immediate refund of the amount paid from your bank or building society". The system is used by millions; it's so common for bill payments that paying by another payment method often attaches an additional charge. [edit] Oh, I guess you mean in the case of a regular payment of an uncertain amount, like a mobile phone bill. I use a pay-as-you-go plan where a direct debit takes a fixed amount out of my account each month, and if I overrun it then my phone stops working until I pay more. I'd definitely think twice before setting up a DD for a mobile phone contract.