NACHA

NACHA (previously the National Automated Clearing House Association) publishes and maintains the NACHA Operating Rules, the rulebook governing all ACH transactions in the US. Every participant in the ACH network, originating depository financial institutions (ODFIs), receiving depository financial institutions (RDFIs), and third-party service providers, must comply with these rules.

ACH transactions originate when a business or individual instructs their bank (ODFI) to send a credit or debit to another bank account. The ODFI submits the transaction to an ACH operator (The Federal Reserve or EPN), which routes it to the RDFI for settlement. NACHA's rules govern every step: authorisation requirements, file formats, return codes, dispute procedures, and timing.

NACHA updates its rules on an annual cycle, with rule changes typically taking effect in March. Merchants and payment providers must monitor NACHA rule updates and adjust their ACH processing practices accordingly. Significant recent updates include Same-Day ACH expansion, rule changes around WEB debit authorisation requirements, and return rate thresholds for ODFIs.

For merchants, the most relevant NACHA rules govern WEB debit authorisations (internet-initiated transactions must be validated before originating), return rate thresholds (ODFIs must monitor and control return rates for the merchants they originate on behalf of), and data security requirements for account numbers used in ACH transactions.

Return rate monitoring is a compliance obligation: NACHA rules set thresholds for ACH return rates that ODFIs must enforce. Merchants with return rates above these thresholds risk having their ACH origination suspended by their ODFI. Understanding and monitoring return codes, particularly unauthorised returns (R10), is operationally necessary for merchants with significant ACH volume.

Account validation reduces unauthorised returns: WEB debit rule changes require that account numbers be validated before the first ACH debit in the WEB entry class. Validation methods include micro-deposit verification, bank account verification APIs, or prenote transactions. Skipping validation increases unauthorised return rates.

Same-Day ACH has changed merchant use cases: NACHA expanded Same-Day ACH to cover debits in addition to credits, enabling near-real-time ACH payment collection for merchants. Same-Day ACH carries a per-transaction fee and has a maximum amount per transaction (currently $1 million).

ACH is US-specific: NACHA rules only apply to US ACH transactions. Non-US account-to-account payment schemes (SEPA in Europe, Faster Payments in the UK, PIX in Brazil) have their own governing bodies and rule sets that are entirely separate from NACHA.