> ## Documentation Index
> Fetch the complete documentation index at: https://docs.bolta.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Tax Invoice Issuance Deadline

> How to call the API that returns the issuance deadline for a tax invoice write date, and how Bolta sets the deadline.

## 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.

<Info>
  This API requires no issuer registration and no certificate, and it deducts no points. Call it with an API key alone.
</Info>

You can issue up to and including the deadline. From the next day on, Bolta does not accept the issuance.

## Request

| Header          | Required | Description                                                                               |
| --------------- | -------- | ----------------------------------------------------------------------------------------- |
| `Authorization` | O        | Set `Basic {apiKey}`. See the [authentication guide](/en/api-introduction/authentication) |

| Query parameter | Required | Description                       |
| --------------- | -------- | --------------------------------- |
| `date`          | O        | Write date in `YYYY-MM-DD` format |

```bash theme={"dark"}
curl "https://xapi.bolta.io/v1/taxInvoiceIssueDueDates?date=YYYY-MM-DD" \
  -H "Authorization: Basic {apiKey}"
```

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.

## Response

```json theme={"dark"}
{
  "date": "YYYY-MM-DD",
  "issueDueDate": "YYYY-MM-DD"
}
```

| Field          | Type   | Description                              |
| -------------- | ------ | ---------------------------------------- |
| `date`         | string | The write date you requested             |
| `issueDueDate` | string | Issuance deadline in `YYYY-MM-DD` format |

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.

## 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`.

<Info>
  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.
</Info>

## Billing and call quota

This API deducts no points and has no separate call quota. You can see your calls in the [Developer Center](https://developers.bolta.io) call logs.

## Errors

| Status code | Error code        | Condition                                                                                                                |
| ----------- | ----------------- | ------------------------------------------------------------------------------------------------------------------------ |
| `400`       | `INVALID_REQUEST` | `date` is missing, is not in `YYYY-MM-DD` format or is not a real date, or falls in a month without a supported deadline |
| `401`       | -                 | API key authentication failed. No response body                                                                          |

For the full list, see [Error Codes](/en/api-introduction/error-codes).

## Related documents

* [Retrieve Tax Invoice Issuance Deadline API](/api-reference/tax-invoice-retrieval/retrieve-tax-invoice-issuance-deadline)
* [Email approval reverse issuance](/en/api-introduction/usecase-reverse-email)
* [Simple approval reverse issuance](/en/api-introduction/usecase-reverse-simple)
* [Error Codes](/en/api-introduction/error-codes)