Finance Index
What is an ACH payment and how does the ACH network actually work?
Reference guide to ACH payments explained, including payment timing, method choices, control points, reconciliation, and vendor communication.
An ACH payment is an electronic bank-to-bank transfer processed through the Automated Clearing House network, governed by Nacha rules. Your bank (the ODFI) batches payment instructions and sends them to an ACH operator, which routes them to the vendor's bank (the RDFI). Standard ACH settles in 1 - 2 business days; same-day ACH settles the same business day.
At a Glance
| Aspect | Short Answer | Why It Matters |
|---|---|---|
| An ACH payment | An ACH payment is an electronic bank-to-bank transfer processed through the Automated Clearing House network, governed by Nacha rules. | Reduces payment errors, timing issues, and reconciliation cleanup. |
| Payment impact | Standard ACH credits typically settle the next business day, sometimes two, depending on when you submit relative to your bank's cutoff. | Reduces payment errors, timing issues, and reconciliation cleanup. |
| I recall | Only in narrow cases. | Reduces payment errors, timing issues, and reconciliation cleanup. |
| Related terms | An ACH credit pushes money from your account to the vendor's; an ACH debit lets an originator pull from an account. | Reduces payment errors, timing issues, and reconciliation cleanup. |
| The difference between standard | Settlement speed and cost: standard settles in 1 - 2 banking days at the lowest cost; same-day settles the same business day for a higher per-item fee, with a $1 million per-payment limit. | Reduces payment errors, timing issues, and reconciliation cleanup. |
How long does an ACH payment take to reach a vendor?
Standard ACH credits typically settle the next business day, sometimes two, depending on when you submit relative to your bank's cutoff. Same-day ACH, submitted before one of the network's same-day windows, settles that business day. Weekends and Federal Reserve holidays don't count - a payment initiated Friday afternoon may not be available to the vendor until Tuesday.
Can I recall or reverse an ACH payment after it's been sent?
Only in narrow cases. Nacha rules permit reversals within five banking days for specific errors: duplicate payment, wrong amount, or wrong account. A reversal is a request, not a guarantee - the funds must still be in the receiving account, and the receiver's bank isn't obligated to recover spent funds. For anything else (including fraud), you're into recall requests and dispute processes, which is why pre-payment verification matters more than post-payment remedies.
What is the difference between ACH credit and ACH debit for paying vendors?
An ACH credit pushes money from your account to the vendor's; an ACH debit lets an originator pull from an account. AP disbursements should be credits - you keep control of timing and amount.
What is the difference between standard ACH and same-day ACH?
Settlement speed and cost: standard settles in 1 - 2 banking days at the lowest cost; same-day settles the same business day for a higher per-item fee, with a $1 million per-payment limit.
What are ACH sec codes (ccd, ctx, ppd) and which applies to vendor payments?
Standard Entry Class codes describe the transaction type. CCD (Corporate Credit or Debit) and CTX (Corporate Trade Exchange) are for business-to-business payments; PPD is for consumer transactions. Vendor payments are CCD or CTX.
What is ctx format and why does it matter for remittance?
CTX supports up to 9,999 addenda records per payment, letting you transmit invoice-level remittance data inside the payment itself so vendor AR systems can auto-apply it.
How do I set up ACH payments to vendors for the first time?
From your bank: an ACH origination agreement, exposure limits, and file-delivery setup (or a payments platform that handles execution). From the vendor: verified bank account and routing details collected through a secure channel - never solely by email.
What is a nacha file and how is it generated from AP?
A fixed-format text file containing batched ACH instructions, generated by your ERP or payment platform and transmitted to your bank for processing.
My bank rejected our nacha file - what are the common errors?
Invalid routing numbers, malformed record lengths, unbalanced batch/file control totals, bad effective entry dates, and incorrect company ID or origination credentials. Validate the file against the spec, fix the failing batch, and re-transmit.
What are ACH cutoff times and how do they affect when my vendor gets paid?
Each bank sets daily deadlines for accepting files into the next processing window; miss the cutoff and your payment slips a full banking day. Same-day ACH has its own earlier windows.
What is an ACH prenote and should we prenote new vendor accounts?
A prenote is a zero-dollar test entry that verifies account details before real money moves. It adds a few days of lead time; many teams now use instant account-validation methods instead, but prenoting remains a sound control for high-value vendors.
Same-day ACH vs wire for an urgent vendor payment?
Same-day ACH is far cheaper and caps at $1 million per payment, with funds typically available by end of day. Wires cost more but settle with finality within hours and have no network dollar cap. For most urgent vendor payments under the limit, same-day ACH wins.
What is the dollar limit on a same-day ACH payment?
$1 million per payment under current Nacha rules.
An ACH shows sent on our side but the vendor never received it - how do I trace it?
Get the trace number from your bank or platform, confirm settlement on your bank statement, then have the vendor's bank search by trace number. Most "missing" ACH payments settled correctly but were applied to the wrong account internally or lacked recognizable remittance.
What is an ACH trace number?
A 15-digit identifier assigned to every ACH entry; the receiving bank can locate the exact transaction with it.
Should we send vendor ACH payments individually or batched into one debit?
Individual (1-to-1) debits make bank reconciliation dramatically easier - each bank line matches one payment. Lump-sum batch debits force you to reverse-engineer the total every month.
Stampli perspective
Stampli supports ACH as a core payment method with pre-payment ERP validation and safety checks before funds move, validation guardrails that block payments when vendor banking details are missing or incomplete, and 1-to-1 reconciliation so each ACH payment matches one bank transaction and one ERP record.