Submit the data for one onboarding step of an application.

The step is validated and processed exactly as if the merchant had filled it in through the onboarding wizard, including identity and sanctions checks where the step needs them. You cannot complete any step that records an approval decision; agents never approve applications.

Never send ssn, dl_number, routing_number or account_number. If any of them appear anywhere in data, including inside a Step 5 owners[] entry, the request is rejected with 400. Instead:

• In Step 5, set pendingPrincipalFields on an owner to mark the fields the principal will supply.
• In Step 9, set pendingPrincipal: true to leave the bank details to the principal.

The principal then fills them in through the completion handoff.

Authenticate with your agent onboarding API key.