Suggest the next invoice number

When to use this endpoint

Use this to prefill a create form. Treat the result as a suggestion: it is not reserved and another writer may use it first.

The request must use a logged-in CRM session or valid signed API credentials and is scoped to that tenant.

Users whose legacy crm_access mask contains bit 64 receive {"error":"no permission to access api"}. No record-owner check is made.

This endpoint has no operation-specific parameters.

$number = FM_api('Invoice_getNumberNext');

"INV-0102"

Response	Condition
`{"error":"not logged in"}`	No authenticated tenant context is available. Invalid signed credentials can be rejected by the dispatcher before the handler runs.

Legacy application errors may be returned with HTTP 200. Check the decoded response for error, not only the HTTP status.

acc-inv-num-method=1 increments the greatest number by length and lexical order; 2 returns a blank string; other values increment the last-created active numbered invoice.
The helper keeps all non-digits as the prefix, increments the combined digits, and preserves their width. No lock or uniqueness reservation is taken.

No direct production CRM1 caller was found for this route.

The Create Invoice dialogs in Invoices and Quotes request this value when the number input is present.