Automated Clearing House (ACH)

What Is Automated Clearing House?

Automated Clearing House (ACH) is the electronic network that batch-processes bank-to-bank transfers across nearly every U.S. financial institution. ACH operators process transactions in batches rather than one by one, as in a wire, and settle them at a predetermined time, usually the next business day. 

In practice, ACH is a common batch-processing service used for payroll, bill payments, vendor payments, and government disbursements. Two ACH operators run the network: the Federal Reserve’s FedACH and The Clearing House’s Electronic Payments Network.

In 2025, the ACH Network processed 35.2 billion payments totaling $93 trillion, and now Nacha must enable every originator on that network to perform risk-based fraud monitoring on all credit entries sent by every originator. For compliance teams, Automated Clearing House payments stopped being a back-office processing detail the moment regulators tied that volume to a mandatory fraud framework. 

How Automated Clearing House Payments Work

Every ACH transaction moves as either a credit or a debit. A credit pushes funds from an originator to a recipient, the mechanism behind payroll deposits, tax refunds, and vendor disbursements. A debit pulls funds from a customer’s account under prior authorization, as in subscription billing, loan repayments, and utility collections.

The originating bank, known as the Originating Depository Financial Institution (ODFI), submits the instruction to an ACH operator, which sorts and batches it before routing it to the Receiving Depository Financial Institution (RDFI) for posting. Standard entries typically settle within one to three business days. Same Day ACH settles within hours, and volume on that faster rail reached 1.4 billion payments worth $3.9 trillion in 2025, up more than 16% from the year before.

What Is the National Automated Clearing House Association (NACHA)?

The National Automated Clearing House Association (NACHA) writes and enforces the operating rules that govern all banks and credit unions participating in the ACH Network. Its rulebook sets standards for authorization, return codes, settlement timing, and, increasingly, fraud controls.

Nacha’s updated risk management framework is now fully in effect. Phase one, effective March 20, 2026, required Originating Depository Financial Institutions and large originators to build risk-based fraud monitoring. Phase two, effective June 22, 2026, extended that requirement to every non-consumer originator, third-party sender, and receiving bank on the network, regardless of transaction volume. Every organization that originates or receives ACH entries now needs a documented, auditable fraud-monitoring process to remain compliant with Nacha’s rules.

Why ACH Payments Are a Growing Compliance Risk

Nacha built its new rules around credit-push fraud: cases where a criminal manipulates an authorized party into initiating a legitimate-looking payment through business email compromise, vendor impersonation, or payroll diversion. Because these transactions carry valid authorization, traditional controls designed to detect unauthorized activity often allow them to pass. Static rules and sanctions screening alone rarely identify payments that appear procedurally correct but deviate from normal customer behavior.

Business-to-business ACH volume alone grew almost 10% in 2025 to 8.1 billion payments, widening the surface area for schemes like this. A compliance program built only around watchlists and sanctions screening misses this pattern, since the fraudulent counterparty rarely appears on any list. What catches it is behavioral monitoring, flagging first-time payees, last-minute changes to banking details, and payment patterns that break from a vendor’s known history.

How AML Watcher Supports ACH Payments Compliance

To meet Nacha’s fraud monitoring requirements, suspicious payment behavior should be identified prior to settlement, not just through sanctions or watchlist screening. AML Watcher’s transaction monitoring includes behavioral analysis, payment screening, and detection rules for defining what constitutes an unusual transaction in an ACH workflow, including payroll diversion attempts, changes in vendor accounts, and more.

The buffer compliance teams that once could stave off suspicious payments during settlement are eliminated by Same Day ACH. As settlement windows continue to shrink, fraud monitoring must keep pace to remain effective.

As ACH settlement becomes faster and fraud monitoring requirements become stricter, many financial institutions struggle to detect authorized payment fraud before funds leave the account. AML Watcher helps compliance teams monitor ACH activity in real time with behavioral analytics, payment screening, and configurable transaction monitoring. 

Request a demo to experience how AML Watcher supports compliant ACH payment monitoring.