Payment rails
ACH
The US automated clearing house, processing transfers in batches over one to two business days.
ACH processes US domestic payments in batches, at very low cost, over one to two business days. The rail works in both directions: an ACH credit pushes funds to an account, an ACH debit pulls from it.
A destination account is identified by a nine-digit routing number and an account number. Unlike an IBAN these carry no overall check digit: a typo can produce a valid pair at another bank, which makes account-name verification particularly important.