> ## Documentation Index > Fetch the complete documentation index at: https://alguna.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Mark a subscription milestone reached > Declares the milestone reached on an active subscription, which releases the one-off prices billing on it onto the billing schedule: each is invoiced on the day of this call, with `reached_at` as its service date. The milestone must be referenced by one of the subscription's prices. Completing a milestone that is already reached returns it unchanged, so the call is safe to retry. ## OpenAPI ````yaml /api-reference/v2/specs/2026-04-01.json post /subscriptions/{id}/milestones/{key}/complete openapi: 3.1.0 info: description: >- Alguna is the AI-native quote-to-revenue platform for B2B companies: CPQ, subscription and usage-based billing, invoicing, payment collection, and revenue recognition in one system of record. The API operates on one versioned agreement per customer: quotes, subscriptions and their versions, usage, invoices, payments, and revenue schedules read from it. Official SDKs: TypeScript (@alguna/sdk), Python (alguna), Go (github.com/alguna-io/alguna-go), Rust (alguna), and the alguna CLI (@alguna/cli). title: Alguna Public API version: '2026-04-01' servers: - url: https://api.alguna.io x-fern-server-name: Production security: - bearerAuth: [] tags: - name: Billing Events and Metrics - name: Checkout Sessions - name: Credit Notes - name: Credits - name: Customer Portal Sessions - name: Customers - name: Feedback - name: Insights - name: Integrations - name: Invoices - name: Merchants - name: Payments - name: Plans - name: Product Bundles - name: Products - name: Quotes - name: Refunds - name: Revenue Schedules - name: Subscription Changes - name: Subscription Versions - name: Subscriptions - name: Tags - name: Tax - name: Users - name: Wallet Grants - name: Wallets paths: /subscriptions/{id}/milestones/{key}/complete: post: tags: - Subscriptions summary: Mark a subscription milestone reached description: >- Declares the milestone reached on an active subscription, which releases the one-off prices billing on it onto the billing schedule: each is invoiced on the day of this call, with `reached_at` as its service date. The milestone must be referenced by one of the subscription's prices. Completing a milestone that is already reached returns it unchanged, so the call is safe to retry. operationId: complete-subscription-milestone parameters: - in: header name: Alguna-Version required: true schema: enum: - '2026-04-01' type: string - in: header name: Idempotency-Key schema: description: >- A unique string that makes a retried write safe. If you send the same request with the same key within 24 hours, the API returns the stored response and does not run the request again. A 5xx or 429 response is not stored, so a retry with that key runs the request again. example: ik_a1b2c3d4e5f6 maxLength: 255 type: string - in: path name: id required: true schema: description: Unique identifier for the subscription type: string - in: path name: key required: true schema: description: Unique identifier for the milestone type: string requestBody: content: application/json: schema: $ref: '#/components/schemas/CompleteMilestoneRequest' required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/SubscriptionMilestoneResponse' description: Success headers: Idempotency-Key: description: Echo of the idempotency key provided in the request schema: type: string Idempotent-Replayed: description: >- Whether this response was replayed from a previous request (true) or freshly executed (false) schema: type: boolean '400': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Bad Request '401': content: application/json: schema: oneOf: - $ref: '#/components/schemas/ErrorResponse' - $ref: '#/components/schemas/GatewayErrorResponse' description: Unauthorized '403': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Forbidden — the organization does not have access to this feature '404': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Not Found '409': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: >- Conflict — a request with this idempotency key is currently being processed headers: Retry-After: description: >- Seconds to wait before retrying with the same idempotency key. Sent only when a request with this key is still being processed; a 409 without it is a conflict that a retry will not resolve. schema: type: integer '422': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Unprocessable Entity '500': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Internal Server Error '502': description: >- Bad Gateway — sent by the infrastructure in front of the API; the body is not JSON. Safe to retry. '503': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: >- Service Unavailable — a dependency is temporarily unavailable. Retry with backoff. '504': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: >- Gateway Timeout — the request did not finish in time. Retry with backoff; use an idempotency key for writes. components: schemas: CompleteMilestoneRequest: properties: note: description: >- Free-text note recorded with the completion, such as a shipment reference example: Shipment DHL-4471 nullable: true type: string reached_at: description: >- The date the milestone was reached (YYYY-MM-DD). Defaults to today; may be backdated to the contract start but never set in the future example: '2026-03-10' nullable: true type: string type: object SubscriptionMilestoneResponse: properties: completed_at: description: >- The day the milestone was declared reached: the invoicing date of the charge format: date-time nullable: true type: string completion_source: description: Which surface declared the milestone reached enum: - dashboard - api nullable: true type: string expected_at: description: When the milestone is expected to be reached; forecasting only format: date-time nullable: true type: string id: description: >- Milestone record ID, set once the milestone has an expected date or has been reached example: smst_01hz... nullable: true type: string key: description: Milestone key the subscription's prices reference example: go_live type: string name: description: Display name example: Go Live type: string note: description: Note recorded with the completion nullable: true type: string price_ids: description: The subscription's prices that bill when this milestone is reached items: type: string type: array reached_at: description: 'The day the milestone was reached: the service date on the charge' format: date-time nullable: true type: string status: description: pending until a completion is recorded, then reached enum: - pending - reached example: pending type: string subscription_id: description: Subscription ID example: sub_01hz... type: string required: - key - name - price_ids - status - subscription_id type: object ErrorResponse: description: The body of every error the API returns. properties: detail: description: Explanation of what went wrong type: string status: description: HTTP status code of the response format: int64 type: integer title: description: >- HTTP status text. Sent only by version, idempotency and credit-refusal errors. type: string type: description: Always `about:blank`. Sent only by version and idempotency errors. type: string required: - status - detail type: object GatewayErrorResponse: description: >- Returned by the API gateway when a request carries no valid API key, before the API handles it. properties: code: description: Machine-readable error code, e.g. `unauthenticated` type: string details: nullable: true type: object message: description: Explanation of what went wrong type: string required: - code - message type: object securitySchemes: bearerAuth: bearerFormat: API Key description: API key authentication. Pass your API key as a Bearer token. scheme: bearer type: http x-fern-bearer: env: ALGUNA_API_KEY name: apiKey ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.