Send ACH Payments and Direct Deposits Through One API
An ACH API lets your software send and receive ACH bank transfers directly, without a person manually entering payment details into a banking portal. Add Same Day ACH and a Direct Deposit API on top of that, so payroll, vendor payments, and disbursements can run straight from your product.
Last updated July 2026
OnlineCheckWriter.com, powered by Zil Money, is a financial technology company and not a bank. Banking services are provided by our partner bank, Member FDIC. FDIC insurance applies only to eligible products associated with those that have funds held in accounts at the partner bank, subject to applicable limits and requirements.
{ "amount": 15000.00, "currency": "USD", "same_day": true, "recipient": { "account_number": "****6721", "routing_number": "****0021" } }
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One API, Four Ways to Move Money
OnlineCheckWriter is a business payments platform for check writing, ACH, wire transfers, and direct deposit. The ACH payment API handles the Nacha file formatting, submission, and status tracking, and sends results back to your system through the API or a webhook.
Single Payments
Send one ACH transfer at a time with an amount, account, and routing number.
Recurring Transfers
Schedule repeat ACH payments for rent, subscriptions, or vendor terms.
Batch Files
Submit an entire payroll or vendor run as one batch instead of one call per payment.
Same Day ACH
Flag a transfer as same-day eligible to settle it before the business day ends.
Send Payments That Settle the Same Business Day
- Processed through three settlement windows the ACH Network runs each business day, under rules set by Nacha, the organization that governs the ACH network.
- Current per-transaction limit is $1,000,000, effective since March 2022. A proposed increase to $10,000,000 targets September 2027 and is not in effect yet.
- Works for domestic, bank-to-bank transfers on business days only. No weekends, no federal holidays, no international payments.
- Our processing bank’s internal cutoff runs earlier than Nacha’s network deadline. Our integration team confirms your exact cutoff when you set up API access.
"same_day": true, "amount": 15000.00, "effective_date": "2026-07-14", // settles same business day if // submitted before your cutoff
Run Payroll and Vendor Deposits From Your Own Platform
The Direct Deposit API is not a separate product. It is the ACH payment API used to originate payroll and vendor deposits on your customers’ behalf, built for software platforms that pay other people’s employees or vendors, not for an individual depositing their own paycheck.
This walkthrough shows an ACH payment moving through a connected bank account inside OnlineCheckWriter, the same underlying processing that powers the ACH API. If you want a ready-made dashboard instead of building your own interface, use OnlineCheckWriter’s Direct Deposit feature. Use the API if you want to embed it directly into your own product.
How to Integrate the ACH API
Get API Access
Access is provisioned per business account. An integration specialist sets up your credentials and confirms your Same Day ACH cutoff time, then gives you sandbox access to test before going live.
Submit Transactions
Send single payments, recurring transfers, or batch files through REST endpoints, flagging Same Day ACH where you need same-business-day settlement.
Track Status
Receive updates through the API or webhooks, so your platform can show whether a payment is pending, settled, or returned, including Notification of Change updates.
Built for Platforms That Move Other People’s Money
Payroll and HR Software
Originate direct deposit for your customers’ employees.
Marketplaces and Gig Platforms
Pay out sellers or contractors on a schedule.
Property Management Software
Collect rent or pay out vendors and owners.
Lending Platforms
Disburse loans and collect repayments.
Accounts Payable Software
Automate vendor payments instead of cutting paper checks.
Insurance and Claims Platforms
Send claims payouts directly to a policyholder’s bank account.
Built on a Platform Held to Real Standards
Every transaction sent through the ACH API runs on Nacha-compliant processing, with bank account and routing numbers encrypted in transit and at rest.
ISO 27001
ISO 20000
Encrypted account data
Nacha-compliant processing
One thing worth knowing before you integrate: under Nacha rules, you, not just the API provider, are responsible for getting authorization from the person you’re paying and keeping it on file, generally for at least two years after the authorization ends. If your use case involves collecting payments rather than sending them, such as rent or loan repayments, that runs as a consumer ACH debit, which carries its own rules, including account validation the first time you debit a new account and Reg E dispute rights for the person you’re debiting. Our integration team walks your team through what applies to your use case.
ACH files are originated through OnlineCheckWriter’s partner banks, listed in the footer of this site. OnlineCheckWriter.com, powered by Zil Money, is a financial technology company and not a bank. Banking services are provided by our partner bank, Member FDIC. FDIC insurance applies only to eligible products associated with those that have funds held in accounts at the partner bank, subject to applicable limits and requirements.
ACH API Frequently Asked Questions
What is an ACH API?
An ACH API is a set of endpoints that lets a software application send and receive ACH bank transfers directly, without a person manually entering payment details into a banking portal.
What is the difference between Same Day ACH and standard ACH?
Standard ACH payments typically settle in one to two business days. Same Day ACH payments submitted before the applicable cutoff settle on the same business day they are submitted.
What is the dollar limit for Same Day ACH?
The current Nacha limit for Same Day ACH is $1,000,000 per transaction, effective since March 2022. A proposed increase to $10,000,000 is not yet in effect.
Does Same Day ACH work on weekends or holidays?
No. Same Day ACH only processes on business days and does not run on weekends or federal holidays.
What is the Direct Deposit API used for?
The Direct Deposit API lets a software platform, such as a payroll or marketplace product, originate direct deposit payments to its own customers’ employees or vendors directly from its application. It uses the same underlying ACH payment API.
Is the ACH API secure and Nacha compliant?
Yes. Transactions run on Nacha-compliant processing with encryption in transit and at rest, and OnlineCheckWriter holds PCI-DSS and ISO 27001 certification.
Does the API support batch payments?
Yes. You can submit a single transaction, a recurring transfer, or a batch file, and flag any of them for Same Day ACH processing where eligible.
How much does the ACH API cost?
ACH API access is provisioned per business account based on transaction volume and use case. Contact our integration team for pricing that fits your platform.
Is there a sandbox to test the API before going live?
Yes. A sandbox environment is available so your team can build and test the integration before sending live transactions.
Ready to Add ACH to Your Product?
Talk to our integration team about your transaction volume, Same Day ACH needs, and existing OnlineCheckWriter account. They will set you up with sandbox credentials and a pricing structure that fits your use case.
OnlineCheckWriter.com, powered by Zil Money, is a financial technology company and not a bank. Banking services are provided by our partner bank, Member FDIC. FDIC insurance applies only to eligible products associated with those that have funds held in accounts at the partner bank, subject to applicable limits and requirements.