Invoices
Generate IRN
POST
/v1/system-integrators/invoices/generate-irn
Generate an Invoice Reference Number (IRN) for an invoice using the FIRS format:
{invoice_number}-{service_id}-{YYYYMMDD}.
| Field | Type | Required | Description |
|---|---|---|---|
| invoice_number | string | Yes | Your invoice number — non-alphanumeric characters are stripped before it's used in the IRN |
| invoice_issue_date | date | Yes | Issue date (YYYY-MM-DD) |
| service_id | string | Yes | FIRS service ID used verbatim as the IRN's middle segment |
| business_id | string | Yes | FIRS business ID of the taxpayer issuing the invoice |
This composes an IRN string client-side (
{invoice_number}-{service_id}-{YYYYMMDD}) — it doesn't
look up or validate the taxpayer/business against FIRS. Make sure service_id matches the
taxpayer's actual firs_service_id before using the result on a real submission.
json
{
"invoice_number": "INV-2025-00045",
"invoice_issue_date": "2025-10-07",
"service_id": "94ND90NR",
"business_id": "3fa85f64-5717-4562-b3fc-2c963f66afa6"
}
json
{
"success": true,
"message": "Success",
"data": { "irn": "INV202500045-94ND90NR-20251007" }
}