attestwireAttestwire › Rule reference › BR-29
BR-29 The invoicing period must not end before it starts
noun · EN 16931 · fatal · BT-73 / BT-74
For a sample invoice, the library reports: The invoicing period runs from "2026-07-31" (BT-73) to "2026-07-01" (BT-74), which ends before it starts. EN 16931 requires the end date to be later than or equal to the start date; equal is allowed, because a single-day period is a real thing.
- Business term
BT-73 / BT-74- Severity
fatal
The fix
Swap invoicingPeriod.startDate and invoicingPeriod.endDate, or correct whichever of the two is wrong. Use the same date in both fields for a period of one day.
A passing value
"invoicingPeriod": { "startDate": "2026-07-01", "endDate": "2026-07-31" }What the library returns
The full error returned by @attestwire/en16931. It includes the rule ID,
affected field and suggested correction. Developers can use this object in their application:
{
"rule": "BR-29",
"field": [
"BT-73",
"BT-74"
],
"severity": "fatal",
"message": "The invoicing period runs from \"2026-07-31\" (BT-73) to \"2026-07-01\" (BT-74), which ends before it starts. EN 16931 requires the end date to be later than or equal to the start date; equal is allowed, because a single-day period is a real thing. An inverted period is almost always two fields transposed, and it is worth catching here rather than downstream: a consumer that computes a duration from it gets a negative number and either books the accrual to the wrong period or divides by it.",
"fix": "Swap invoicingPeriod.startDate and invoicingPeriod.endDate, or correct whichever of the two is wrong. Use the same date in both fields for a period of one day.",
"example": "\"invoicingPeriod\": { \"startDate\": \"2026-07-01\", \"endDate\": \"2026-07-31\" }",
"xpath": "/ubl:Invoice/cac:InvoicePeriod/cbc:EndDate",
"docsUrl": "https://attestwire.com/rules/BR-29"
}
xpath is always a UBL path. On a CII invoice, look for the
matching CII field instead.