Treasury Prime Alternative for Payment APIs | OnlineCheckWriter

Payment API

A Treasury Prime Alternative for Teams That Need Payment APIs

Send ACH payments, domestic and international wires, from one platform, without building a broader banking infrastructure stack.

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OnlineCheckWriter.com – powered by Zil Money, is a financial technology company, not a bank. Banking and money movement services are provided through partner financial institutions and licensed service providers. FDIC insurance coverage applies only to eligible deposit products and accounts, and is subject to applicable terms, conditions, limitations, and requirements. Additional information regarding partner institutions, products, and services is available in the applicable terms and agreements.

One API
wire.json
// One API for ACH and wires
{
  "method": "wire",
  "amount": "12,500.00",
  "destination": "international",
  "status": "sent"
}
REST API
Sandbox included
PHP · Node.js · Python SDKs

Illustrative example. See the API docs for exact request format.

No sponsor-bank build required

ACH and wire payments, one integration

Some teams evaluating a banking-as-a-service platform only need to move money, not stand up a sponsor-bank relationship, account-issuing program, or compliance stack. OnlineCheckWriter covers the payment-execution piece.

ACH API

Send ACH credits and debits with one call. Same Day ACH available; your integration team confirms your cutoff during setup. Payment status updates through the API or webhooks.

Wire API

Send domestic wire transfers through the API or the dashboard. Wire timing and fees vary by destination and are confirmed with your integration team.

International Wire

Send wire transfers to bank accounts outside the United States through the same API used for domestic wires. Timing and fees vary by destination and are confirmed with your integration team.

Sandbox & SDKs

Test in a sandbox environment before you go live. Public PHP, Node.js, and Python SDKs are available.

Scope

Where this fits in your stack

May fit if you need

ACH payments, domestic or international wires, or bulk business payments combined in one integration.

A full banking platform may fit better if you need

A sponsor-bank relationship, your own account-issuing program, or compliance and risk infrastructure built for a banking-as-a-service model.

Moving over

Move ACH and wire workflows in three steps

Start with the payment method you use most, and expand from there.

Open a sandbox account

Test ACH and wire workflows before any production traffic moves.

Map your current payment rails

Note which ACH or wire flows, domestic and international, you want to bring over first.

Verify and go live

Your integration specialist confirms account setup, then you’re in production.

Domestic and cross-border

ACH and wire, without a banking-program build

Send payments through one integration instead of standing up separate rails for domestic and international transfers.

  • Bulk Payment API sets the method per payee, ACH, check, wire, or card
  • Recurring ACH runs for repeat vendor payments
  • Role-based permissions across your team
  • Full payment history in one dashboard
GET/capabilities200 OK
{
  "ach": { "same_day": true },
  "wire": {
    "domestic": true,
    "international": true
  },
  "bulk_payment_api": {
    "methods": ["ach", "wire", "check", "card"]
  }
}
FAQ

Payment API questions, answered

ACH

What is OnlineCheckWriter’s ACH API?
A REST API for sending ACH credits and debits programmatically. It supports single, recurring, and batch payments.
Is there a limit on Same Day ACH transactions?
The Nacha ACH network sets a $1,000,000 per-transaction ceiling for Same Day ACH, effective since March 2022. Your specific account limit is confirmed with your integration team and may be lower than the network ceiling. A $10,000,000 network ceiling has been proposed for September 2027; it is not in effect yet.

Wire

What is OnlineCheckWriter’s Wire API?
A REST API and dashboard option for sending domestic wire transfers.
How long does a wire take, and what does it cost?
Wire timing and fees vary by destination and receiving bank. Current rates and typical timing are confirmed with your integration team.

International

Does OnlineCheckWriter support international wires?
Yes. International wire transfers send funds to bank accounts outside the United States, through the same API used for domestic wires. Timing and fees vary by destination and are confirmed with your integration team.

Account & Security

Is OnlineCheckWriter Nacha compliant?
Yes. OnlineCheckWriter is an official Nacha member, and the platform holds PCI-DSS and ISO 27001 certifications.
How is my data secured?
OnlineCheckWriter’s platform uses encryption in transit and at rest, and holds PCI-DSS and ISO 27001 certifications.

Switching & Migration

Can I combine ACH and wire payments in one integration?
Yes. The Bulk Payment API sets the payment method per payee, combining ACH, check, wire, and card in a single integration.
Can I start with only ACH or only wires?
Yes. Payment methods can be integrated individually rather than all at once. Production access and migration timing are confirmed with the integration team.
Can I test before migrating anything?
Yes. Sandbox access is available before any production account or verification is required.
Does OnlineCheckWriter replace a direct FedACH connection?
No. OnlineCheckWriter is a payment API built on existing banking rails, not a direct Federal Reserve connection or bank charter.

Try it first

See if a payment API covers what you actually need

Test ACH and wire workflows in sandbox, or talk to an integration specialist about your setup.

Get API Access
Book a Demo