openapi: 3.2.0
info:
  title: Abstract VAT Validation Calculate API
  description: 'Validate a VAT number and retrieve the registered company details, calculate VAT-compliant prices for a given amount and country, and look up the latest VAT rates and reduced-rate categories for a country. Authenticate with your API key as the `api_key` query parameter, or as an `Authorization: Bearer ` header. GET and POST (form-encoded or JSON) are both supported.'
  version: 1.0.0
  termsOfService: https://www.abstractapi.com/legal/legal
  contact:
    name: Abstract API
    url: https://www.abstractapi.com/api/vat-validation-rates-api
  license:
    name: Commercial — see Terms of Service
    url: https://www.abstractapi.com/legal/legal
servers:
- url: https://vat.abstractapi.com/v1
security:
- ApiKeyQuery: []
- BearerAuth: []
tags:
- name: Calculate
paths:
  /calculate:
    get:
      operationId: getCalculateVat
      summary: Calculate VAT for an amount
      description: Determines VAT-compliant prices for a given value, country, and purchase type.
      parameters:
      - name: amount
        in: query
        required: true
        description: The amount that you would like to get the VAT amount for or from.
        schema:
          type: string
        example: '175'
      - name: country_code
        in: query
        required: true
        description: The two-letter ISO 3166-1 alpha-2 code of the country in which the transaction takes place.
        schema:
          type: string
        example: DE
      - name: is_vat_incl
        in: query
        required: false
        description: Set to true if the amount already includes VAT and you would like to perform the reverse calculation. Defaults to false.
        schema:
          type: boolean
        example: false
      - name: vat_category
        in: query
        required: false
        description: The category of goods or services, used when a country offers a reduced VAT rate for certain categories.
        schema:
          type: string
        example: standard
      responses:
        '200':
          description: The calculated VAT-inclusive and VAT-exclusive amounts.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/VatCalculation'
              example:
                amount_excluding_vat: '175.00'
                amount_including_vat: '208.25'
                vat_amount: '33.25'
                vat_category: standard
                vat_rate: '0.190'
                country:
                  code: DE
                  name: Germany
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '422':
          $ref: '#/components/responses/QuotaReached'
        '429':
          $ref: '#/components/responses/TooManyRequests'
        '500':
          $ref: '#/components/responses/ServerError'
      tags:
      - Calculate
    post:
      operationId: postCalculateVat
      summary: Calculate VAT for an amount
      description: 'Same as the GET operation. The API key may be supplied in the request body, as the `api_key` query parameter, or as an `Authorization: Bearer ` header.'
      requestBody:
        required: true
        content:
          application/x-www-form-urlencoded:
            schema:
              $ref: '#/components/schemas/CalculateRequest'
          application/json:
            schema:
              $ref: '#/components/schemas/CalculateRequest'
      responses:
        '200':
          description: The calculated VAT-inclusive and VAT-exclusive amounts.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/VatCalculation'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '422':
          $ref: '#/components/responses/QuotaReached'
        '429':
          $ref: '#/components/responses/TooManyRequests'
        '500':
          $ref: '#/components/responses/ServerError'
      tags:
      - Calculate
components:
  responses:
    QuotaReached:
      description: Unprocessable — monthly quota reached or insufficient API credits. The body follows the standard error envelope.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    TooManyRequests:
      description: Too Many Requests — rate limit exceeded (free plans are limited to 1 request per second). The body follows the standard error envelope.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    BadRequest:
      description: Bad request — a required parameter is missing or failed validation.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            error:
              message: A validation error occurred.
              code: validation_error
              details:
                vat_number:
                - This is a required argument.
    ServerError:
      description: Internal server error. The body follows the standard error envelope.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    Unauthorized:
      description: Unauthorized — missing or invalid API key.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            error:
              message: Invalid API key provided.
              code: unauthorized
              details: null
  schemas:
    VatCalculation:
      type: object
      properties:
        amount_excluding_vat:
          type:
          - string
          - 'null'
          description: The transaction amount before VAT.
          example: '175.00'
        amount_including_vat:
          type:
          - string
          - 'null'
          description: The transaction amount with VAT included.
          example: '208.25'
        vat_amount:
          type:
          - string
          - 'null'
          description: The VAT portion of the amount.
          example: '33.25'
        vat_category:
          type:
          - string
          - 'null'
          description: The category of goods or services used for the calculation; null when no specific category applies.
          example: standard
        vat_rate:
          type:
          - string
          - 'null'
          description: The VAT rate applied, expressed as a decimal fraction.
          example: '0.190'
        country:
          type:
          - object
          - 'null'
          description: The country in which the transaction takes place.
          properties:
            code:
              type:
              - string
              - 'null'
              description: The two-letter ISO 3166-1 alpha-2 code of the country.
            name:
              type:
              - string
              - 'null'
              description: The name of the country.
    Error:
      type: object
      required:
      - error
      properties:
        error:
          type: object
          required:
          - message
          - code
          properties:
            message:
              type: string
              description: Human-readable description of the error.
              example: A validation error occurred.
            code:
              type: string
              description: Machine-readable error code, e.g. validation_error or unauthorized.
              example: validation_error
            details:
              type:
              - object
              - 'null'
              description: Field-keyed validation messages for validation_error responses; null for other error types.
              additionalProperties:
                type: array
                items:
                  type: string
    CalculateRequest:
      type: object
      required:
      - amount
      - country_code
      properties:
        amount:
          type: string
          description: The amount that you would like to get the VAT amount for or from.
          example: '175'
        country_code:
          type: string
          description: The two-letter ISO 3166-1 alpha-2 code of the country in which the transaction takes place.
          example: DE
        is_vat_incl:
          type: boolean
          description: Set to true if the amount already includes VAT and you would like to perform the reverse calculation. Defaults to false.
          example: false
        vat_category:
          type: string
          description: The category of goods or services, used when a country offers a reduced VAT rate for certain categories.
          example: standard
        api_key:
          type: string
          description: 'Your API key. Optional here if supplied as the `api_key` query parameter or an `Authorization: Bearer <key>` header.'
  securitySchemes:
    ApiKeyQuery:
      type: apiKey
      in: query
      name: api_key
      description: Your unique VAT Validation API key.
    BearerAuth:
      type: http
      scheme: bearer
      description: Send your API key as a Bearer token; omit `api_key` from the query string.
externalDocs:
  description: Official documentation
  url: https://docs.abstractapi.com/api/vat-validation
x-openItems:
- The exact code and message strings for the 422 (quota reached / insufficient credits), 429 (rate limit) and 500 (server error) responses are unconfirmed. The error envelope shape is modeled from the documented 400/401 examples, but the literal code and message values for these statuses are not verified against production.
- Which response fields can truly return null is assumed generously per the nullability convention and needs production confirmation. Specifically, this spec marks VatCalculation.amount_excluding_vat, amount_including_vat, vat_amount and vat_rate as nullable, and VatCategory.rate and category as nullable; these assumptions need backend confirmation.
- Whether VatValidation.company and VatValidation.country can be null on a valid VAT lookup (and which of their sub-fields can be null) is assumed and needs production confirmation.
- The calculate and categories docs label the monetary/rate fields (amount_excluding_vat, amount_including_vat, vat_amount, vat_rate, and VatCategory.rate) as Float, but the documented JSON examples return them as quoted strings (e.g. '175.00', '0.190', '0.070'). They are modeled as type:string to match the actual wire format; the Float-vs-string discrepancy needs backend confirmation.
- CORS support is unknown and needs confirmation.