> ## Documentation Index > Fetch the complete documentation index at: https://docs.numeral.com/llms.txt > Use this file to discover all available pages before exploring further. # Update Customer > Update an existing customer's information ## Update Customer Endpoint (2026-11-01) Update an existing customer's `name`, `email`, `is_tax_exempt` status, or `reference_customer_id`. All fields are optional, but at least one must be provided. Only the fields you include are changed; everything else is left as is. > [!NOTE] > > Remember to include the `X-API-Version: 2026-11-01` header in your request to use this API version. > [!NOTE] > > The `customer_id` path parameter accepts either the Numeral customer ID (`cust_xxx`) or your own `reference_customer_id`. No `id_type` query parameter is needed. ### Behavior * `email` and `reference_customer_id` must be unique across your customers. If another customer already uses the new value, the request fails with `DUPLICATE_CUSTOMER`. * `email` must be a valid email address, otherwise the request fails with `INVALID_EMAIL`. * Setting `is_tax_exempt` to `true` means all future `POST /tax/calculations` for this customer return \$0 in tax owed. Setting it to `false` removes the exemption. * If every provided value matches what is already stored, nothing is written and the current customer is returned with a `200`. * Deleted customers cannot be updated. The request fails with `CUSTOMER_NOT_FOUND`. * If the customer's buyer record has been deleted in Numeral's Exemption Certificate Manager, setting `is_tax_exempt` to `true` is rejected with `INVALID_REQUEST`. ```bash cURL (mark tax exempt) theme={null} curl -X POST https://api.numeralhq.com/tax/customers/cust_6126acaf-7379-411a-8ada-00005bac0715 \ -H "Authorization: Bearer sk_test_xxx" \ -H "X-API-Version: 2026-11-01" \ -H "Content-Type: application/json" \ -d '{ "is_tax_exempt": true }' ``` ```bash cURL (by reference ID) theme={null} curl -X POST https://api.numeralhq.com/tax/customers/20506 \ -H "Authorization: Bearer sk_test_xxx" \ -H "X-API-Version: 2026-11-01" \ -H "Content-Type: application/json" \ -d '{ "name": "New Customer Name", "email": "new.email@example.com" }' ``` ```json 200 - Success theme={null} { "id": "cust_6126acaf-7379-411a-8ada-00005bac0715", "object": "tax.customer", "reference_customer_id": "20506", "name": "New Customer Name", "email": "new.email@example.com", "is_tax_exempt": true } ``` ```json 400 - Duplicate theme={null} { "code": 400, "type": "DUPLICATE_CUSTOMER", "message": "Customer already exists." } ``` ```json 400 - Not Found theme={null} { "code": 400, "type": "CUSTOMER_NOT_FOUND", "message": "Customer with id cust_9876543210abcdef not found" } ``` ## OpenAPI ````yaml api-reference/v2026-11-01/openapi.json POST /tax/customers/{customer_id} openapi: 3.0.1 info: title: Numeral API description: >- API for sales tax calculations - Version 2026-11-01. This version adds a `note` to every tax jurisdiction row and an `effective_tax_rate` to calculations and platform calculation totals. license: name: MIT version: '2026-11-01' servers: - url: https://api.numeralhq.com/ security: - bearerAuth: [] paths: /tax/customers/{customer_id}: post: summary: Update Customer description: >- Update an existing customer's information. All fields are optional, but at least one must be provided. Only the fields you include are changed. operationId: updateCustomer_v20261101 parameters: - name: customer_id in: path required: true schema: type: string description: >- The Numeral customer ID (`cust_xxx`) or your `reference_customer_id`. Either identifier is accepted; no `id_type` query parameter is needed. requestBody: content: application/json: schema: $ref: '#/components/schemas/CustomerUpdateRequest' examples: mark_tax_exempt: summary: Mark a customer as tax exempt value: is_tax_exempt: true update_contact_info: summary: Update name and email value: name: New Customer Name email: new.email@example.com update_reference_id: summary: Change the reference customer ID value: reference_customer_id: '20507' required: true responses: '200': description: The updated customer content: application/json: schema: $ref: '#/components/schemas/CustomerResponse' '400': description: >- Invalid request. Returned when no updatable field is provided (`INVALID_REQUEST`), the email is malformed (`INVALID_EMAIL`), the customer does not exist or has been deleted (`CUSTOMER_NOT_FOUND`), or another customer already uses the new `email` or `reference_customer_id` (`DUPLICATE_CUSTOMER`). content: application/json: schema: $ref: '#/components/schemas/Error' components: schemas: CustomerUpdateRequest: type: object description: >- Request body for updating a customer. All fields are optional, but at least one must be provided. properties: name: type: string description: The customer's name example: New Customer Name email: type: string description: The customer's email. Must be unique across your customers. example: new.email@example.com is_tax_exempt: type: boolean description: >- If true, all `POST /tax/calculations` sold to this customer will return $0 in tax owed. example: true reference_customer_id: type: string description: >- The ID of the customer in your system. Must be unique across your customers. example: '20507' CustomerResponse: type: object properties: id: type: string description: The ID of the customer example: cust_123456789 object: type: string description: 'The type of object: `tax.customer`' example: tax.customer reference_customer_id: type: string description: The ID of the customer in your system example: '20506' name: type: string description: The name of the created customer example: Customer Name email: type: string description: The email of the created customer example: customer@example.com is_tax_exempt: type: boolean description: >- If true, all `POST /tax/calculations` sold to this customer will return $0 in tax owed. The default value is `false`. example: true Error: type: object description: Standard error response format for API version 2026-01-01 properties: code: type: integer description: HTTP status code example: 400 type: type: string description: Machine-readable error type example: MISSING_FIELD message: type: string description: Human-readable error message example: Required field 'address_country' is missing required: - code - type - message securitySchemes: bearerAuth: type: http scheme: bearer ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.