> ## Documentation Index > Fetch the complete documentation index at: https://docs.meum.io/llms.txt > Use this file to discover all available pages before exploring further. # Start payment link checkout > Creates or reuses an invoice for this payment link and returns a hosted checkout URL. No API key required. Rate limited per buyer token. **Fixed amount:** omit `amount` when the link uses `fixed_amount` mode. **Customer-defined amount:** send `amount` as a decimal string within the link min/max. **Single-use links:** a second checkout reuses the open invoice when one exists; paid single-use links return `403`. ## OpenAPI ````yaml /openapi.yaml post /v1/public/payment-links/{public_id}/checkout openapi: 3.1.0 info: title: Meum Public Merchant API version: 1.0.0 description: > Public merchant API for programmatic payment management: invoices, transactions, payment links, webhooks, and WooCommerce integration. Authenticate with a store-scoped API key (`sk_live_*`) via Bearer token. Base URL: https://api.meum.io contact: name: Meum Support email: support@meum.io url: https://meum.io servers: - url: https://api.meum.io description: Production security: - bearerAuth: [] tags: - name: Health description: Service health checks - name: Invoices description: Invoice lifecycle - name: Transactions description: On-chain payment transactions - name: Payment Links description: Reusable payment link management - name: Webhooks description: Webhook endpoint and delivery management - name: Integrations description: Third-party platform integrations paths: /v1/public/payment-links/{public_id}/checkout: post: tags: - Payment Links summary: Start payment link checkout description: > Creates or reuses an invoice for this payment link and returns a hosted checkout URL. No API key required. Rate limited per buyer token. **Fixed amount:** omit `amount` when the link uses `fixed_amount` mode. **Customer-defined amount:** send `amount` as a decimal string within the link min/max. **Single-use links:** a second checkout reuses the open invoice when one exists; paid single-use links return `403`. operationId: startPublicPaymentLinkCheckout parameters: - $ref: '#/components/parameters/PaymentLinkBuyerPublicId' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/PublicPaymentLinkCheckoutRequest' examples: fixedAmount: summary: Fixed amount link value: origin_asset: usdc.near refund_to: alice.near customerAmount: summary: Customer-defined amount value: amount: '42.50' origin_asset: usdc.near refund_to: alice.near responses: '201': description: Checkout session created content: application/json: schema: $ref: '#/components/schemas/PublicPaymentLinkCheckoutResponse' '400': $ref: '#/components/responses/BadRequest' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' '429': $ref: '#/components/responses/RateLimited' '503': $ref: '#/components/responses/ServiceUnavailable' security: [] components: parameters: PaymentLinkBuyerPublicId: name: public_id in: path required: true description: > Public checkout token from the Pay Link's `public_id` field (starts with `plpub_`). Share this in checkout URLs; do not confuse with the merchant `plink_` ID. schema: type: string pattern: ^plpub_[0-9a-z]{20,32}$ example: plpub_c9a9bb730611077574c828af5af5fed1 schemas: PublicPaymentLinkCheckoutRequest: type: object required: - origin_asset - refund_to properties: amount: type: string description: > How much to charge the customer, as a decimal string (e.g. `"42.50"`). **Required** when the Pay Link uses `customer_defined_amount`. **Omit** when the link has a fixed price; the link's amount is used automatically. example: '42.50' origin_asset: type: string description: | **Required.** Which crypto the customer will pay with. Format: `token.network`: e.g. `usdc.near` means USDC on NEAR. example: usdc.near refund_to: type: string description: > **Required.** Wallet address to send refunds to if payment fails or the customer overpays. Must be valid on the same network as `origin_asset` (e.g. `alice.near` for NEAR). example: alice.near PublicPaymentLinkCheckoutResponse: type: object required: - invoice_id - checkout_url - reused properties: invoice_id: type: string pattern: ^(inv_|txn_|plink_|wh_|whd_|evt_|int_)[0-9a-z]{20,32}$ description: >- New or existing invoice for this checkout (`inv_...`). Use to track payment status. checkout_url: type: string format: uri description: Open this URL in a browser to show the payment page to the customer. reused: type: boolean description: > `true`: an unpaid invoice from a previous attempt was reused (common for single-use links). `false`: a brand-new invoice was created. PublicApiError: type: object description: Standard error envelope for Public API v1 endpoints. required: - error properties: error: type: object description: Error details for the failed request. required: - type - code - message - request_id properties: type: type: string description: High-level error category used for programmatic handling. enum: - invalid_request - authentication_error - permission_error - not_found - conflict - rate_limit_error - api_error example: not_found code: type: string description: >- Stable machine-readable error code (for example `invoice_not_found`). example: invoice_not_found message: type: string description: Human-readable explanation suitable to show in logs or UI. example: Invoice not found param: type: string description: Request field associated with the error, when applicable. example: url request_id: type: string description: Unique request ID. Include when contacting support. example: req_a1b2c3d4e5f6789012345678 example: error: type: not_found code: invoice_not_found message: Invoice not found request_id: req_a1b2c3d4e5f6789012345678 responses: BadRequest: description: Invalid request content: application/json: schema: $ref: '#/components/schemas/PublicApiError' Forbidden: description: Insufficient scope or permission content: application/json: schema: $ref: '#/components/schemas/PublicApiError' NotFound: description: Resource not found content: application/json: schema: $ref: '#/components/schemas/PublicApiError' RateLimited: description: Rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/PublicApiError' ServiceUnavailable: description: Store or platform not ready to accept payments content: application/json: schema: $ref: '#/components/schemas/PublicApiError' securitySchemes: bearerAuth: type: http scheme: bearer description: | Store-scoped API key. Prefix with `sk_live_`. Example: `Authorization: Bearer sk_live_EXAMPLE_DO_NOT_USE` ````