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

# Validate invoice number

> Check whether an invoice number is available (not already in use) for your legal entity.



## OpenAPI

````yaml get /invoice/validate-number
openapi: 3.1.0
info:
  title: Slash Public API
  description: API description
  version: 0.0.1
  contact: {}
servers:
  - url: https://api.slash.com
    description: production
security:
  - api_key: []
  - partner_api_key: []
  - bearer: []
  - developer_application: []
paths:
  /invoice/validate-number:
    get:
      description: >-
        Check whether an invoice number is available (not already in use) for
        your legal entity.
      parameters:
        - name: filter:legalEntityId
          description: >-
            The legal entity ID to check the invoice number against. Required if
            authenticating with access to multiple legal entities.
          in: query
          required: false
          schema:
            type: string
        - name: invoiceNumber
          in: query
          required: true
          description: The invoice number to validate.
          schema:
            type: string
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                type: object
                properties:
                  isAvailable:
                    type: boolean
                    description: Whether the invoice number is available for use.
                required:
                  - isAvailable
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '403':
          description: Forbidden
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '429':
          description: TooManyRequests
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '500':
          description: Internal Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      security:
        - api_key: []
        - bearer: []
components:
  schemas:
    Error:
      type: object
      properties:
        message:
          type: string
        name:
          type: string
        identifier:
          type: string
        rawStatus:
          type: number
        meta:
          type: object
          additionalProperties: true
      required:
        - message
        - name
        - identifier
        - rawStatus
      x-entrypoint:
        origin: ./src/publicApi
        sourcePath: ./src/publicApi/main.yaml
        title: Error
        virtualPath: components/Error
      title: Error
  securitySchemes:
    api_key:
      type: apiKey
      description: |
        API key authentication for public API requests.

        Keys come in two flavors:

        - *Legal-entity-scoped keys* are pinned to a single legal entity.
          Minted via the dashboard under a specific entity; every request
          acts on that entity.
        - *User-scoped keys* are pinned to a user and span every legal
          entity that user has access to. Every request made with a
          user-scoped key (except `GET /legal-entity`, which lists the
          legal entities the user can access) must include an
          `x-legal-entity` header naming the legal entity the request is
          operating on. Requests without the header are rejected with
          `400`. The authenticated user must have an active permission
          role on the supplied legal entity, otherwise the request is
          rejected with `403`.
      name: X-API-Key
      in: header
    partner_api_key:
      type: apiKey
      description: |
        Partner-program API key authentication.

        Keys are minted in the partner dashboard (Developers → API Keys),
        are scoped to a single partner program, and are prefixed with
        `sk_partner_`. Partner keys are only accepted by routes that
        declare this scheme; they are rejected by `api_key` routes and
        vice versa.
      name: X-API-Key
      in: header
    bearer:
      type: http
      scheme: bearer
    developer_application:
      type: http
      scheme: basic

````