transfer systems where the transfer of money or securities takes place from one bank to another on a "real-time" and on "gross" basis. Settlement in "real time" means that payment transaction does not require any waiting period. The transactions are settled as soon as they are processed. "Gross settlement" means the transaction is settled on one to one basis without bunching or netting with any other transaction. Once processed, payments are final and irrevocable.

Comparatively, ACHs are typically used for low-value, non-urgent transactions