# Add a tax ID to your account

> The portal.tax_ids.add operation: POST /api/v1/portal/me/tax_ids in the REST API and the portal_tax_ids_add tool in the MCP server.

Adds a tax ID (for example an EU VAT number) to the signed-in customer's account after checking it with its
register (VIES for EU VAT IDs, HMRC for UK VAT numbers, the Swiss UID register; others by format). The answer is
stored with it: a number the register doesn't know is kept as `invalid` and doesn't make purchases
business-to-business. A malformed number is refused (`tax_id_invalid`). At most 5 per customer.

Emits `customer.updated`. Customer portal only (`portal:write`).

## At a glance

- **REST:** `POST /api/v1/portal/me/tax_ids`
- **MCP tool:** `portal_tax_ids_add`
- **Operation ID:** `portal.tax_ids.add`
- **Scope:** Brand
- **Permission:** `portal:write`
- **Risk tier:** `write`
- **Dry run:** Not supported
- **Idempotency:** `Idempotency-Key` required
- **Modes:** Test and live
- **Authentication:** A customer signed in to the customer portal (API keys can't call it)
- **Since:** M9

## Request

### Body

A JSON object (`Content-Type: application/json`):

| Field     | Type   | Required | Description                                                                                                                                        |
| --------- | ------ | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------- |
| `type`    | string | Yes      | The tax ID's type: `eu_vat`, `gb_vat`, `ch_uid`/`ch_vat`, `no_org`/`no_vat` or `us_ein`. Other types are kept but can't be checked (`unverified`). |
| `value`   | string | Yes      | The number as the customer gave it, with or without the country prefix and separators.                                                             |
| `country` | string | Yes      | The country that issued the tax ID (ISO 3166-1 alpha-2; `EL` = Greece).                                                                            |

## Response

`201 Created` with a JSON object:

| Field                | Type                                                                  | Description                                                                              |
| -------------------- | --------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| `object`             | `"portal_account"`                                                    |                                                                                          |
| `customerId`         | `cus_…` ID                                                            |                                                                                          |
| `livemode`           | boolean                                                               |                                                                                          |
| `email`              | string                                                                |                                                                                          |
| `name`               | string or null                                                        |                                                                                          |
| `businessName`       | string or null                                                        |                                                                                          |
| `type`               | one of `individual`, `business`, `unknown`                            |                                                                                          |
| `locale`             | string or null                                                        |                                                                                          |
| `billingAddress`     | object or null                                                        |                                                                                          |
| `taxIds`             | array of object                                                       |                                                                                          |
| `taxIds[].id`        | string                                                                | The tax ID's identity on your account: its canonical number.                             |
| `taxIds[].type`      | string                                                                |                                                                                          |
| `taxIds[].value`     | string                                                                |                                                                                          |
| `taxIds[].country`   | string                                                                |                                                                                          |
| `taxIds[].status`    | one of `valid`, `invalid`, `unavailable`, `format_only`, `unverified` | The register's answer: `valid`, `invalid`, `unavailable`, `format_only` or `unverified`. |
| `taxIds[].checkedAt` | date-time                                                             |                                                                                          |
| `portalLastLoginAt`  | date-time or null                                                     |                                                                                          |

## Examples

### Add an Austrian VAT ID

```http
POST /api/v1/portal/me/tax_ids
Authorization: Bearer or_test_…
Idempotency-Key: 3f1c9a52-7d0e-4b8f-9a61-0c2d5e8b7f14
Content-Type: application/json

{
  "type": "eu_vat",
  "value": "ATU 0000 0000",
  "country": "AT"
}
```

Response (`201`):

```json
{
  "object": "portal_account",
  "customerId": "cus_01m4tx5nj8emwbyf7y9vcf48b1",
  "livemode": false,
  "email": "ana@example.com",
  "name": "Ana Novak",
  "businessName": "Alpen Apps GmbH",
  "type": "business",
  "locale": null,
  "billingAddress": {
    "line1": "Ring 1",
    "line2": null,
    "city": "Wien",
    "postalCode": "1010",
    "region": null,
    "country": "AT"
  },
  "taxIds": [
    {
      "id": "ATU00000000",
      "type": "eu_vat",
      "value": "ATU00000000",
      "country": "AT",
      "status": "valid",
      "checkedAt": "2026-10-20T09:00:00.000Z"
    }
  ],
  "portalLastLoginAt": "2026-10-20T09:00:00.000Z"
}
```

## Errors

| Code                                                                                             | HTTP status | When                                                                                                                  | What to do                                                                                                                                                          |
| ------------------------------------------------------------------------------------------------ | ----------- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`validation_failed`](https://ownrecord.io/docs/reference/errors.md#validation_failed)           | 400         | A field is missing or malformed.                                                                                      | Fix the fields listed in `details.issues` and send the request again.                                                                                               |
| [`tax_id_invalid`](https://ownrecord.io/docs/reference/errors.md#tax_id_invalid)                 | 400         | The number isn't valid for its type and country (format or checksum); `details.reason` says which. Nothing is stored. | Check the number and its country for typing errors (`details.reason` says what is wrong), then send it again. A Northern Ireland business enters its GB VAT number. |
| [`customer_deleted`](https://ownrecord.io/docs/reference/errors.md#customer_deleted)             | 400         | Your account was deleted by the brand.                                                                                | Create a new customer for this buyer. Deleted customers stay readable for the records they belong to, but can't be changed.                                         |
| [`customer_tax_id_exists`](https://ownrecord.io/docs/reference/errors.md#customer_tax_id_exists) | 409         | You already have this tax ID.                                                                                         | Nothing to do: the tax ID is already on the customer (`details.tax_id_id`). To check it again, remove it and add it back.                                           |
| [`customer_tax_id_limit`](https://ownrecord.io/docs/reference/errors.md#customer_tax_id_limit)   | 400         | You already have 5 tax IDs.                                                                                           | Remove a tax ID the customer no longer uses before adding another (at most 5 per customer).                                                                         |
| [`version_conflict`](https://ownrecord.io/docs/reference/errors.md#version_conflict)             | 409         | Your details changed at the same moment; retry.                                                                       | Fetch the object again and retry the change.                                                                                                                        |
| [`livemode_not_allowed`](https://ownrecord.io/docs/reference/errors.md#livemode_not_allowed)     | 403         | The portal session is in the other mode than the request.                                                             | Use test mode, or credentials for the target's mode. Developers need live access granted by an organization owner or admin.                                         |
| [`permission_denied`](https://ownrecord.io/docs/reference/errors.md#permission_denied)           | 403         | The caller isn't a customer signed in to this brand's portal (operators and API keys use the customer operations).    | Ask an organization owner or admin for a role or scope that allows this action.                                                                                     |

It can also return these [common errors](https://ownrecord.io/docs/reference.md#common-errors): [`api_version_unsupported`](https://ownrecord.io/docs/reference/errors.md#api_version_unsupported), [`invalid_json`](https://ownrecord.io/docs/reference/errors.md#invalid_json), [`unsupported_media_type`](https://ownrecord.io/docs/reference/errors.md#unsupported_media_type), [`authentication_required`](https://ownrecord.io/docs/reference/errors.md#authentication_required), [`api_key_invalid`](https://ownrecord.io/docs/reference/errors.md#api_key_invalid), [`scope_required`](https://ownrecord.io/docs/reference/errors.md#scope_required), [`resource_not_found`](https://ownrecord.io/docs/reference/errors.md#resource_not_found), [`idempotency_key_required`](https://ownrecord.io/docs/reference/errors.md#idempotency_key_required), [`idempotency_key_reused`](https://ownrecord.io/docs/reference/errors.md#idempotency_key_reused), [`idempotency_in_progress`](https://ownrecord.io/docs/reference/errors.md#idempotency_in_progress), [`dry_run_not_supported`](https://ownrecord.io/docs/reference/errors.md#dry_run_not_supported), [`rate_limited`](https://ownrecord.io/docs/reference/errors.md#rate_limited), [`internal_error`](https://ownrecord.io/docs/reference/errors.md#internal_error).