> ## Documentation Index > Fetch the complete documentation index at: https://docs.avatcado.com/llms.txt > Use this file to discover all available pages before exploring further. # Validate a VAT number asynchronously > Submit a VAT number for asynchronous validation. Returns 202 immediately. The result is delivered to your configured webhook URL when processing is complete. Invalid VAT formats are rejected immediately (422), never queued. Pro and Business tiers only. Requires a configured webhook URL. Test keys are rejected. ## OpenAPI ````yaml /openapi/public.yaml post /v1/validate/async openapi: 3.1.0 info: title: Avatcado API version: '1.0' description: >- Validate VAT and GST numbers across 32 countries with a single API call. Get company details, consultation numbers, and validity status from VIES, HMRC, BFS, BRREG, and ABR, with caching, rate limiting, and structured error responses built in. contact: name: Avatcado url: https://docs.avatcado.com servers: - url: https://api.avatcado.com description: Production security: [] paths: /v1/validate/async: post: tags: - Async Validation summary: Validate a VAT number asynchronously description: >- Submit a VAT number for asynchronous validation. Returns 202 immediately. The result is delivered to your configured webhook URL when processing is complete. Invalid VAT formats are rejected immediately (422), never queued. Pro and Business tiers only. Requires a configured webhook URL. Test keys are rejected. operationId: asyncValidateVatNumber requestBody: content: application/json: schema: $ref: '#/components/schemas/AsyncSingleRequest' responses: '202': description: Validation request accepted for processing content: application/json: schema: $ref: '#/components/schemas/AsyncSingleResponse' '400': description: No webhook URL configured content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: webhook_not_configured message: >- Configure a webhook URL before using async validation. See https://docs.avatcado.com/webhooks docs_url: https://docs.avatcado.com/errors/webhook_not_configured meta: request_id: 550e8400-e29b-41d4-a716-446655440000 '401': description: Invalid or missing API key content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: unauthorized message: Missing or invalid API key docs_url: https://docs.avatcado.com/errors/unauthorized meta: request_id: 550e8400-e29b-41d4-a716-446655440000 '403': description: >- Async validation requires Pro or Business tier, or the key is a test key content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: tier_insufficient message: Async validation requires a Pro or Business plan docs_url: https://docs.avatcado.com/errors/tier_insufficient meta: request_id: 550e8400-e29b-41d4-a716-446655440000 '422': description: Invalid VAT number format content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: invalid_vat_format message: >- The VAT number format is invalid. Expected format: CC123456789 docs_url: https://docs.avatcado.com/errors/invalid_vat_format meta: request_id: 550e8400-e29b-41d4-a716-446655440000 '429': description: Monthly quota or burst rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: code: rate_limit_exceeded message: Monthly validation limit exceeded docs_url: https://docs.avatcado.com/errors/rate_limit_exceeded meta: request_id: 550e8400-e29b-41d4-a716-446655440000 security: - bearerAuth: [] components: schemas: AsyncSingleRequest: type: object properties: vat_number: type: string minLength: 1 description: The VAT number to validate asynchronously example: DE123456789 requester_vat_number: type: string description: Your own VAT number (for consultation numbers) example: NL987654321B01 cache: type: boolean default: true description: Whether to use cached results example: true required: - vat_number AsyncSingleResponse: type: object properties: data: type: object properties: request_id: type: string description: Unique identifier for this async request example: 550e8400-e29b-41d4-a716-446655440000 status: type: string enum: - pending example: pending vat_number: type: string description: The normalized VAT number example: DE123456789 required: - request_id - status - vat_number meta: $ref: '#/components/schemas/ResponseMeta' required: - data - meta ErrorResponse: type: object properties: error: $ref: '#/components/schemas/ErrorDetail' meta: $ref: '#/components/schemas/ResponseMeta' required: - error - meta ResponseMeta: type: object properties: request_id: type: string example: 550e8400-e29b-41d4-a716-446655440000 description: Unique identifier for this request cached: type: boolean description: Whether this result was served from cache cached_at: type: string description: >- When the result was originally cached (only present when cached is true) stale: type: boolean description: >- Whether this is a stale cache result served because the upstream was unavailable source_status: type: string enum: - live - unavailable - degraded description: >- Upstream data source reliability. 'live' = confirmed fresh result. 'unavailable' = upstream source was down, stale cache served. 'degraded' = result may be unreliable (possible silent false negative from VIES, BFS, or BRREG). example: live mode: type: string enum: - test description: Present with value 'test' when using an avat_test_ API key request_duration_ms: type: integer description: Total request processing time in milliseconds example: 120 required: - request_id ErrorDetail: type: object properties: code: type: string description: Machine-readable error code example: missing_parameter message: type: string description: Human-readable error message example: Query parameter 'vat_number' is required docs_url: type: string description: Link to documentation for this error code example: https://docs.avatcado.com/errors/missing_parameter required: - code - message ````