Instant ACH fields added to the Account schema

Broker API

Adds Instant ACH support to accounts. Two new fields are surfaced on the account schemas:

• allow_instant_ach indicates whether the account is eligible for Instant ACH.
• instant_ach_blocked indicates whether Instant ACH is currently blocked for the account.

These fields appear when creating, retrieving, and updating accounts.

Affected Endpoints

• POST /v1/accounts
• GET /v1/accounts
• GET /v1/accounts/{account_id}
• PATCH /v1/accounts/{account_id}