Record an effective-dated change to the interest configuration of an account. Send only the interest parameters you want to change, together with the date on which the change takes effect. The change is appended to the account's history of configuration changes, which you can retrieve with Get account interest.

Key features:

• Updates only the provided parameters. A parameter that is omitted is left untouched, and a parameter sent as null clears the account-level value so the interest plan value applies.
• Applies from effective_date and, optionally, up to end_date. After end_date, the configuration that applied before the change takes effect again.
• Allows overlapping changes. For each parameter, the most recently created change that covers a date determines the value that applies on that date.
• Validates the resulting configuration for every date from today onward and rejects the request with 400 when it is invalid.
• Rejects requests that contain no interest parameter, only dates and metadata.

Once an account has a configuration change, PUT /v1/interest/account/{accountId} is rejected for that account with 409.

Account identification. The token identifies the account. Exactly one of x-account-id or x-external-account-id must be passed and must match the {accountId} path parameter. Otherwise the request is rejected (403 on a mismatch or when neither header is passed, 400 when both are).

Stored identifiers. Which identifiers are stored follows the header used:

• x-account-id: An Accounts API call confirms the account ID exists, then account_id is stored with the change.
• x-external-account-id: A Corporate API call resolves the external account ID to a Pismo account_id, and both IDs are stored with the change.

If the Accounts or Corporate API cannot resolve the identifier the request fails with 400 and nothing is persisted. Any other failure of those APIs fails with 500.

Idempotency. If a change was already recorded with the same x-cid for the organization, the request succeeds without recording a second change.

When a new change is recorded, the endpoint publishes an interest_account_update_success event.

{
  "benchmark": "FED",
  "margin_rate": 1.3,
  "margin": 0.05,
  "effective_date": "2026-11-01",
  "end_date": "2026-12-31",
  "metadata": {
    "campaign": "year-end-promotion"
  }
}

{
  "interest_parameters": {
    "benchmark": "FED",
    "margin_rate": 1.3,
    "margin": 0.05
  },
  "effective_date": "2026-11-01",
  "end_date": "2026-12-31",
  "created_at": "2026-10-14T15:04:05.123456",
  "metadata": {
    "campaign": "year-end-promotion"
  }
}