> ## Documentation Index > Fetch the complete documentation index at: https://docs.ionicfi.com/llms.txt > Use this file to discover all available pages before exploring further. # Retrieve an invoice ## OpenAPI ````yaml /openapi/invoices.yaml get /invoices/{id} openapi: 3.0.3 info: title: Ionic Invoices API version: '2026-05-30' description: | Invoices and invoice items. An invoice item is a pending charge recorded against a customer. When an invoice is created for that customer, every pending item in the invoice currency is drained onto the new draft as a line. A draft can be edited freely; finalizing it assigns a gapless, per-merchant/mode sequential number (for example `INV-000001`), applies tax, freezes the lines, and opens the invoice. Drafts carry no number, so an abandoned draft never consumes one and the finalized sequence is always contiguous. All monetary amounts are integers in the currency's minor unit (for example cents for USD). Timestamps are Unix epoch seconds. Identifiers are opaque, prefixed strings: invoices are `inv_…`, invoice items `ii_…`, and invoice lines `il_…`. Authentication uses a merchant secret key as a bearer token. Read endpoints require the `invoices:read` permission; write endpoints require `invoices:write`. The mode of the key (test or live) scopes which invoices and invoice items it can see, mutate, and drain. Live invoice numbers use `INV-000001` style labels; test invoice numbers use `TEST-INV-000001`. Mutating endpoints accept an optional `Idempotency-Key` header. Errors are returned as `{ "error": { "code": "...", "message": "..." } }`. A malformed path identifier returns 400. Concurrent updates are retried automatically; if they still conflict, the API returns 409 and the request can be retried. servers: - url: '{baseUrl}/v1' variables: baseUrl: default: https://api.ionicfi.com description: API base URL for your environment. security: - secretKey: [] tags: - name: Invoices description: Create, finalize, and manage invoices. - name: Invoice Items description: Pending charges that drain onto a customer's next invoice. paths: /invoices/{id}: parameters: - $ref: '#/components/parameters/InvoiceId' get: tags: - Invoices summary: Retrieve an invoice operationId: invoices_retrieve responses: '200': description: The invoice. content: application/json: schema: $ref: '#/components/schemas/Invoice' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/InvoiceNotFound' '429': $ref: '#/components/responses/RateLimited' '500': $ref: '#/components/responses/InternalError' security: - secretKey: - invoices:read components: parameters: InvoiceId: name: id in: path required: true description: The invoice id (`inv_…`). schema: type: string schemas: Invoice: type: object required: - allow_save_card - amount_paid - amount_remaining - attempt_count - collection_method - created_at - currency - customer - id - lines - metadata - number - object - status - subtotal - tax - total - updated_at properties: id: type: string description: The invoice id (`inv_…`). object: type: string enum: - invoice description: Always `invoice`. number: type: string nullable: true description: >- The gapless per-merchant number, assigned at finalize. Null while draft. customer: type: string description: The billed customer (`cus_…`), set at creation and immutable. subscription: type: string nullable: true description: >- The subscription that generated this invoice (`sub_…`). Absent for one-off invoices created directly against a customer. status: type: string enum: - draft - open - paid - void - uncollectible description: >- One of `draft` (being built, lines mutable, never customer-visible), `open` (finalized, lines frozen, awaiting payment), `paid` (terminal; reachable from `open`, from `uncollectible` via a late payment, or directly at finalize when the total is zero), `void` (terminal; requires `amount_paid` of zero), or `uncollectible` (written off; not terminal, since a late payment can still move it to `paid`). collection_method: type: string enum: - charge_automatically - send_invoice description: >- One of `charge_automatically` (charged automatically against the pinned payment method) or `send_invoice` (the buyer pays the hosted page by `due_date`). collection_payment_method_id: type: string nullable: true description: >- The payment method (`pm_…`) pinned for automatic collection. Null when no method is pinned. allow_save_card: type: boolean description: >- Whether the hosted invoice page offers the buyer the option to save their card for future use. currency: type: string description: >- Three-letter ISO currency code. USD, EUR, and GBP are supported; all use 2-decimal minor units. lines: type: array items: $ref: '#/components/schemas/InvoiceLine' description: The invoice's line items. Frozen once the invoice leaves `draft`. subtotal: type: integer description: The sum of the line amounts, in minor units. tax: type: integer description: >- The tax amount, in minor units. Zero until finalize supplies a tax amount. total: type: integer description: >- `subtotal` plus `tax` minus discounts, in minor units. Discounts can reduce this to zero but never below it. amount_paid: type: integer description: The cumulative amount paid so far, in minor units. amount_remaining: type: integer description: '`total` minus `amount_paid`, in minor units.' due_date: type: integer nullable: true description: >- Unix epoch seconds by which the buyer must pay. Used with `send_invoice`; null otherwise. finalized_at: type: integer nullable: true description: >- Unix epoch seconds when the invoice was finalized. Null while the invoice is a draft. paid_at: type: integer nullable: true description: >- Unix epoch seconds when the invoice became fully paid. Null until then. voided_at: type: integer nullable: true description: >- Unix epoch seconds when the invoice was voided. Null unless the invoice is void. next_payment_attempt_at: type: integer nullable: true description: >- Unix time of the next scheduled automatic collection retry. Present only while a dunning retry is pending. payment_intent: type: string nullable: true description: >- The payment intent created to collect this invoice (`pi_…`). Present once a collection attempt has created one; links the invoice to its transaction. attempt_count: type: integer description: >- The number of collection attempts recorded against this invoice so far. max_attempts: type: integer nullable: true description: >- The dunning policy's total attempt allowance, for rendering progress like "attempt N of max_attempts". Present only on subscription `charge_automatically` invoices when the dunning schedule is enabled for the deployment; null otherwise. hosted_invoice_url: type: string nullable: true description: >- The buyer-facing hosted invoice page URL. Present once the invoice has been finalized and hosted invoicing is enabled for the deployment; null on drafts or when hosted invoicing is not configured. metadata: type: object additionalProperties: type: string description: >- A string key-value map for storing your own structured data. Up to 50 keys; each key at most 40 characters and each value at most 500 characters. created_at: type: integer description: Unix epoch seconds when the invoice was created. updated_at: type: integer description: Unix epoch seconds when the invoice was last updated. InvoiceLine: type: object required: - amount - currency - description - id - quantity - unit_amount properties: id: type: string description: The invoice line id (`il_…`). description: type: string description: The line's label, shown on the invoice. quantity: type: integer description: The quantity of the line item. At least 1. unit_amount: type: integer description: The per-unit price, in minor units. amount: type: integer description: >- The line's total amount, in minor units. Equal to `unit_amount` times `quantity` unless the line is a proration or has an explicit override. currency: type: string description: >- The line's currency. Always matches the invoice's currency; a mismatch is rejected at construction. invoice_item: type: string nullable: true description: Source invoice item, when the line came from a drain. price: type: string nullable: true description: >- The catalog price (`price_…`) this line was derived from, when applicable. Null when the line was added directly. Error: type: object properties: error: type: object properties: code: type: string description: A stable, machine-readable error code. message: type: string responses: BadRequest: description: The request was malformed or failed validation. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: INVALID_DATA message: invalid currency Unauthorized: description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/Error' Forbidden: description: The key lacks the required permission, or the merchant is not active. content: application/json: schema: $ref: '#/components/schemas/Error' InvoiceNotFound: description: No invoice with that id is visible to this key. content: application/json: schema: $ref: '#/components/schemas/Error' example: error: code: INVOICE_NOT_FOUND message: invoice not found RateLimited: description: Too many requests. Honour the `Retry-After` header before retrying. content: application/json: schema: $ref: '#/components/schemas/Error' InternalError: description: | The API could not return a successful response. For a mutating request, retrieve the resource before retrying because the operation may have completed. content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: secretKey: type: http scheme: bearer description: 'A merchant secret key (`sk_…`) sent as `Authorization: Bearer `.' ````