QuickBooks Online: invoice Balance is read-only, update the lines instead

QuickBooks Online calculates invoice Balance from transaction business logic and treats the field as read-only; a supplied value is overwritten. Change editable invoice inputs that determine the amount due, such as the applicable line items, rather than trying to set Balance directly.

After the update, read the invoice again and check the returned Balance. It can also reflect payments against the transaction, so compare the returned invoice and related payment state before diagnosing a failed update.

Intuit’s Invoice API reference marks Balance read-only, says it initially reflects TotalAmt, is calculated by QuickBooks business logic, and any supplied value is overwritten. Updating editable invoice inputs such as lines is the practical implication of the derived field; the linked reference does not describe every invoice-update workflow. Source: https://developer.intuit.com/app/developer/qbo/docs/api/accounting/most-commonly-used/invoice