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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.
This API requires no issuer registration and no certificate, and it deducts no points. Call it with an API key alone.
You can issue up to and including the deadline. From the next day on, Bolta does not accept the issuance.

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Request

Replace YYYY-MM-DD with the write date you want to check. This endpoint does not use Bolta-Client-Reference-Id. 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.
Bolta maintains these dates month by month on its servers and answers only for the months it maintains. Any other month returns 400 with INVALID_REQUEST.
When a new public holiday is declared or the NTS extends a deadline, Bolta updates its servers. The API returns the deadline as of the call, so 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. You can see your calls in the Developer Center call logs.

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Errors

For the full list, see Error Codes.