How to create a custom payment app for specific merchants?

Topic summary

Request to build a custom Shopify payment app limited to a specific merchant. The goal is to enable that merchant to accept payments through the requester’s own gateway.

Primary issue: The requester cannot find clear, official steps or procedures for creating such a custom payment app.

Ask: Guidance on the required process, setup, and how to grant the merchant access to the gateway via a custom app.

Status: No responses or concrete outcomes provided; the thread remains open with unanswered questions.

Context: “Custom payment app” suggests a private payment integration tailored for a single merchant rather than a public app, and clarity on implementation steps is sought.

Summarized with AI on February 26. AI used: gpt-5.

Dear Team,

We are trying to build a custom payment app for a specific merchant and would like to give them access to accept payments through our gateway. We are trying to see the steps and procedures to create a custom payment app, but there are no clear procedures that we can follow.

Can anyone help us with creating a custom payment app?

Thanks a lot!

Lunu