Term · Automated Clearing House

ACH

Published May 9, 2026

Definition

ACH — the Automated Clearing House — is the US bank-to-bank electronic money-movement network operated by NACHA. It handles roughly 30 billion transactions per year including direct deposit, bill payment, brokerage account funding, RIA advisory-fee debits, and corporate-to-corporate B2B payments. Standard ACH settles on a 1-3 business-day window; same-day ACH is available for an additional fee.

ACH is the workhorse of US money movement outside the wire and card rails. For wealth-tech platforms, it's the primary mechanism for funding brokerage accounts (incoming ACH from customer's bank), paying RIA advisory fees (outgoing ACH from customer's brokerage to RIA's operating account), and many B2B flows.

The network operates on a batch-and-net model: institutions submit batches of transactions to ACH operators (the Federal Reserve's FedACH or The Clearing House's EPN), the operators net the transactions across all participants, and settlement happens at the operator level. This batch model is the reason ACH takes 1-3 business days — each batch is processed at fixed times during the day, and settlement happens at end-of-cycle.

Same-day ACH, available since 2016 with multiple processing windows added since, allows transactions submitted before specific cutoffs to settle the same business day. It has higher per-transaction fees and lower per-transaction limits but is increasingly used for time-sensitive flows like RIA fee billing and investor-facing rebates. Real-time alternatives — RTP (Real-Time Payments) operated by The Clearing House, and FedNow operated by the Federal Reserve — are growing but haven't yet displaced ACH for the bulk of wealth-tech use cases.

The failure modes of ACH are well-known and routinely produce wealth-tech bugs: returned items (insufficient funds, wrong account number, account closed) come back days after the original transaction, requiring the platform to handle the un-settle event correctly. ACH same-day cutoffs are time-zone-dependent and aren't always handled correctly in platforms that assume the customer-facing 'submit by 6pm' translates to a specific ACH cutoff. Holiday and weekend handling has its own conventions that test data has to model.

Why this matters for synthetic data

Realistic synthetic data for ACH-driven flows needs to include returned-item scenarios (typically 0.3-0.6% of consumer ACH debits return for insufficient funds; lower for direct-debit pulls from previously-funded accounts), same-day vs. standard-cycle cases, and the 1-3 business-day pending state between submission and settlement. A test corpus that treats ACH as instantaneous money movement has not exercised the pending-state code path and will have idempotency bugs on returned items.

Common pitfalls

Treating ACH as instantaneous — the 1-3 business-day pending state is real and the platform has to surface it correctly to users (and not commit downstream actions, like trade execution, until settlement).
Not handling ACH returns — returned items can come back up to 60 days after origination for some return types; the platform's reconciliation logic has to handle the un-settle event.
Mishandling time-zone for same-day ACH cutoffs — the cutoffs are in Eastern Time and the system's customer-facing UTC-or-local-time logic has to translate correctly.
Confusing ACH with wire transfer — wires are real-time, irrevocable, and have different fee structures; ACH is batched, returnable for ~60 days, and cheaper. Platforms that use one when they should use the other create operational issues.

Examples

ACH transaction lifecycle

Customer initiates a $5,000 transfer from their bank to brokerage on Tuesday at 2pm ET. Standard ACH cutoff is 5:30pm ET; the transaction is included in Tuesday's evening batch. Settlement is Wednesday (T+1). The funds appear in the brokerage as 'pending' on Tuesday evening, 'available for trading' on Wednesday morning. If the customer's bank account had insufficient funds, the return comes back Wednesday-Thursday and the brokerage's reconciliation logic has to reverse the funding entry — including any trade activity the customer may have already initiated against the (now-returned) deposit.

Frequently asked questions

When should I use ACH vs. wire transfer?+

ACH for routine, scheduled, or batch transactions where 1-3 business-day settlement is acceptable: payroll, recurring bill pay, advisory-fee billing, brokerage account funding. Wire for time-sensitive, high-value, irrevocable transactions: large investment purchases, real-estate closings, urgent business-to-business transfers. ACH is typically free or low-fee per transaction; wires are $15-$50 per outgoing wire at most institutions. ACH transactions are returnable for ~60 days; wires are essentially irrevocable once executed.

What's the difference between ACH credit and ACH debit?+

ACH credit is a 'push' — the originator's bank pushes funds to the receiver's bank. Direct deposit and B2B payments are typically ACH credit. ACH debit is a 'pull' — the receiver's bank requests funds from the originator's bank with prior authorization. Direct debit, recurring bill pay, and advisory-fee billing are typically ACH debit. The two have different return-code semantics and different fraud-prevention concerns.

How does same-day ACH work?+

NACHA operates three same-day ACH processing windows during the business day (10:30am, 2:45pm, 4:45pm ET). Transactions submitted before each cutoff settle the same business day at the next settlement window. Same-day ACH has higher per-transaction fees (typically $0.50-$1.00 vs. ~$0.20 for standard) and limits ($1M per transaction as of 2025, increased over time). For wealth-tech, same-day ACH is increasingly used for time-sensitive flows where wire transfer would be overkill but T+1 standard ACH is too slow.