Check Printing & Mailing API

Print & Mail Checks, Straight From Your Application

Create checks, choose print or mail, and get status updates through the OnlineCheckWriter API. Built for teams that want check writing inside their own product instead of a separate login.

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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.

API ready

// create a check, then send it to print or mail

POST /checks

payee, amount, bank_account,

delivery: “print” | “mail”

// check status comes back to your app

GET /checks/{id}

Built for integration

Check printing and mailing as an API

Give your application the ability to create a check and decide how it gets delivered, without sending users to a separate portal.

Create Checks by API

Generate a check from your application with the payee, amount, and paying account you specify.

Print or Mail, Your Call

Route each check to print-ready output, or hand it to the mailing service starting at $1.25 per check via USPS, or $24.99 for FedEx Overnight.

Status Updates

Check on delivery status so your application always knows where a check stands.

Test Before You Go Live

Ask your account team about sandbox and test-mode access before you build against production.

Getting started

From API key to delivered check

The full reference lives in the API docs. Here’s the shape of the flow.

Authenticate

Create a check

Send payee, amount, and bank account details from your application.

Choose delivery

Mark it for print, or hand it to the mailing service.

Track status

Query the API for delivery status as the check moves through.

Why build on it

Keep check writing inside your product

Useful if you’re building accounting software, a vertical SaaS platform, or an internal tool and don’t want to send users somewhere else to cut a check.

No MICR toner or special printer required on the print path
Mailing available without building your own USPS integration
Full reference and authentication details in the API docs
Your account team can confirm test-mode access before you build

Mailing options

First Class$1.25/check

First Class + Tracking$8.10/check

Priority Mail$17.54/check

Express Mail$37.79/check

Certified Mail$9.99/check

FedEx Overnight$24.99/check

No subscription fee. You pay per check mailed. Rates as published on our mailing page; confirm current pricing before quoting a customer.

FAQ

Developer questions, answered

Where do I find the full API reference?

The API documentation is at apiv3.onlinecheckwriter.com. This page covers the shape of what’s possible; the docs cover the exact endpoints and fields.

Is there a sandbox or test mode?

Ask your account team about sandbox and test-mode access as part of onboarding, before you build against production.

How does authentication work?

API access is tied to your OnlineCheckWriter account and an API key. Full setup steps are in the API docs.

Do I still need MICR toner for printed checks?

No special MICR toner is required. The MICR line is generated as part of the check design and prints with any standard toner or ink, on any standard laser or inkjet printer. Banks have processed checks as images since the Check 21 Act, which is why standard printer ink works instead of magnetic ink.

How does mailing pricing work?

You pay per check mailed. USPS First Class is $1.25, First Class with tracking is $8.10, Priority Mail is $17.54, Express Mail is $37.79, Certified Mail is $9.99, and FedEx Overnight is $24.99. There is no subscription fee.

Can I talk to someone before I start building?

Yes, book a demo and we can walk through what your integration would look like.

Start building

See what a check printing and mailing integration looks like

Book a demo to talk through your use case, or jump straight into the API docs.