> ## Documentation Index > Fetch the complete documentation index at: https://www.finseed.es/docs/llms.txt > Use this file to discover all available pages before exploring further. # Download an invoice PDF > Returns a signed `download_url` you can hand straight to a browser to download the invoice PDF, so your API key never reaches the client. The link is a same-origin URL on the API host and stays valid for 24 hours, long enough to embed in a page; request a fresh one once it expires. This endpoint authenticates your integration, not your end users: it can reach every invoice in the key's environment, so check in your own app that the signed-in user may see this invoice before calling it. Every invoice has a PDF. This endpoint returns a signed `download_url` to it. The link stays valid for 24 hours, shown in `expires_at` — long enough to embed in a page your own client opens later. Request a fresh one once it expires rather than storing it indefinitely. There are two common ways to use it: * **Download invoices to your own systems.** Page through the [list of invoices](/docs/api-reference/pagination), then call this endpoint for each one and save the PDF on your side. This runs server to server, behind your API key. * **Let your users download an invoice.** When a user clicks "download" in your app, call this endpoint from your backend and redirect the browser to `download_url`. Your API key stays on your server, and the browser only ever sees the short-lived link. This endpoint authenticates your integration, not your end users: your API key can reach every invoice in its environment. Before you return an invoice to a signed-in user, check in your own application that the invoice belongs to them. ## OpenAPI ````yaml GET /v1/invoices/{id}/download openapi: 3.1.0 info: title: Finseed API version: 1.0.0 description: >- REST API for programmatic Verifactu invoicing. Every request is sent over HTTPS and authenticated with an API key passed as a bearer token. Each key is scoped to a single environment (test or live). Payloads are JSON with snake_case fields: amounts are integer minor units (cents) and timestamps are RFC 3339 in UTC. List endpoints are cursor-paginated. Errors return a small application/json envelope with a stable, machine-readable `code`. servers: - url: https://api.finseed.es security: - bearerAuth: [] paths: /v1/invoices/{id}/download: get: tags: - Invoices summary: Download an invoice PDF description: >- Returns a signed `download_url` you can hand straight to a browser to download the invoice PDF, so your API key never reaches the client. The link is a same-origin URL on the API host and stays valid for 24 hours, long enough to embed in a page; request a fresh one once it expires. This endpoint authenticates your integration, not your end users: it can reach every invoice in the key's environment, so check in your own app that the signed-in user may see this invoice before calling it. operationId: downloadInvoice parameters: - name: id in: path required: true description: Opaque invoice identifier — the `id` from a list row. schema: type: string responses: '200': description: A signed link to download the invoice PDF. content: application/json: schema: $ref: '#/components/schemas/InvoiceDownload' '401': description: >- Authentication failed: the API key is missing, malformed, or revoked. Send a valid key as a bearer token in the `Authorization` header. Each key is bound to a single environment (test or live). content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' example: code: unauthorized detail: >- Authentication failed. Send your API key as a bearer token in the `Authorization` header. Keys are scoped to one environment, so a test key cannot read live data and vice versa. errors: [] doc_url: https://www.finseed.es/docs/api-reference/errors#unauthorized '404': description: >- No invoice matches the supplied identifier in the environment the API key belongs to. An invoice created with a live key is not visible to a test key, and vice versa. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' example: code: invoice_not_found detail: >- No invoice matches that identifier in this environment. Note that test and live keys see different invoices. errors: [] doc_url: >- https://www.finseed.es/docs/api-reference/errors#invoice_not_found '500': description: >- An unexpected error occurred on our side. No partial work is persisted, so the request can be retried safely. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' example: code: internal_error detail: >- Something went wrong on our side. The request did not complete and can be retried safely. errors: [] doc_url: >- https://www.finseed.es/docs/api-reference/errors#internal_error components: schemas: InvoiceDownload: type: object properties: download_url: type: string description: >- Signed URL on the API host that returns the invoice PDF. Hand it straight to a browser to download the file. It stays valid for 24 hours, so you can embed it in a page; request a fresh one once it expires. example: https://api.finseed.es/v1/invoices/inv_clx123abc456/file?token=… filename: type: string description: Suggested file name for the downloaded PDF. example: 2026-000123.pdf expires_at: type: string description: >- When download_url stops working, RFC 3339 in UTC. Request a fresh link after this. example: '2026-06-02T08:35:00Z' required: - download_url - filename - expires_at additionalProperties: false description: A signed link to download an invoice as a PDF. example: download_url: https://api.finseed.es/v1/invoices/inv_clx123abc456/file?token=… filename: 2026-000123.pdf expires_at: '2026-06-02T08:35:00Z' ErrorEnvelope: type: object properties: code: type: string description: >- Stable, machine-readable error code. The branch key. This is an extensible enum: new values may be added in the future, so clients must tolerate values not listed here. Known values: invalid_request, unauthorized, invoice_not_found, download_link_expired, number_series_not_found, number_series_prefix_taken, number_series_in_use, customer_not_found, customer_ambiguous, idempotency_conflict, rate_limited, invalid_number_series, invalid_tax_rate, invalid_tax_data, invalid_tax_id, tax_id_type_country_mismatch, insufficient_recipient_data, simplified_amount_exceeded, simplified_incompatible_tax_type, invalid_recargo_equivalencia, aeat_mandate_not_approved, no_active_subscription, tax_id_validation_unavailable, invalid_rectifies_reference, rectified_invoice_not_found, invoice_already_voided, invoice_already_replaced, invoice_not_family_tip, invoice_pending_at_aeat, invoice_not_rectifiable_at_aeat, family_balance_below_zero, replacement_total_negative, reason_incompatible_with_recipient, recipient_overrides_not_allowed_for_differences, rectifying_series_invalid, external_reference_invalid, external_reference_matches_existing_invoice, rectified_amounts_required_for_substitution, line_item_without_tax_items, internal_error. example: invalid_request detail: type: string description: Human-readable, context-specific explanation. example: The query parameters are not valid. errors: type: array items: type: object properties: field: type: string description: Location of the offending value (JSON path). example: limit code: type: string description: Machine-readable validation issue code. example: too_big message: type: string description: Human-readable explanation of the field-level issue. example: Number must be less than or equal to 100 required: - field - code - message additionalProperties: false description: >- Field-level issues. Always present; empty unless this is a validation failure. doc_url: type: string description: Link to the reference documentation for this error code. example: https://www.finseed.es/docs/api-reference/errors#invalid_request required: - code - detail - errors - doc_url additionalProperties: false description: >- Uniform error body returned for every non-2xx response (application/json). securitySchemes: bearerAuth: type: http scheme: bearer description: API key sent as a bearer token in the `Authorization` header. ````