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What this API returns

GET /v1/taxInvoiceIssueDueDates takes a write date and returns the issuance deadline for a tax invoice with that date. The issuance and reverse issuance request APIs already check the write date against the deadline when they receive a request and return 400 if the date is out of range. Call this API when you need the deadline ahead of time, for example to show it in your UI or to check a write date before issuing.
Call this API with an API key alone, without issuer registration, a certificate, or Bolta-Client-Reference-Id.
You can issue up to and including the deadline.

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Request

Replace YYYY-MM-DD with the write date you want to check. Test and live keys return the same result.

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Response

For example, a write date of September 30, 2026 returns an issueDueDate of October 12, 2026. October 10 is a Saturday, so the deadline moves to the next business day.

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How the deadline is set

The deadline is the 10th of the month after the write date.
  • If the 10th falls on a weekend or public holiday, the deadline is the next business day.
  • When the National Tax Service (NTS) extends the deadline for a month, the extended date applies. For write dates in September 2025, the deadline is October 15, 2025.
For a month without a supported deadline, the API returns 400 with INVALID_REQUEST.
The API returns the deadline as of the call. Query it again when you need it instead of storing the result long term.

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Billing and call quota

This API deducts no points and has no separate call quota. Check your calls in the Developer Center call logs.

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Errors

For the full list, see Error Codes.