> ## Documentation Index > Fetch the complete documentation index at: https://docs.flextell.ai/llms.txt > Use this file to discover all available pages before exploring further. # Add payment to a sale > Requires `Pay:Sale`. Without `ViewAllSales:Sale` only the caller's own sales are accepted; any other sale returns 404. On an installment sale, `installment_number` links the collection to that installment; the collections linked to one installment cannot exceed its amount. ## OpenAPI ````yaml post /v1/sales/{id}/payments openapi: 3.1.0 info: title: Flextell API version: 0.0.1 description: >- Flextell REST API referansı. Kimlik doğrulama, scope ve istek kuralları için API sekmesindeki rehberlere bakın. servers: - url: https://app.flextell.ai/api description: Üretim security: - oauth2: [] - bearer: [] paths: /v1/sales/{id}/payments: post: tags: - Sales summary: Add payment to a sale description: >- Requires `Pay:Sale`. Without `ViewAllSales:Sale` only the caller's own sales are accepted; any other sale returns 404. On an installment sale, `installment_number` links the collection to that installment; the collections linked to one installment cannot exceed its amount. operationId: sales.addPayment parameters: - name: id in: path required: true description: The sale identifier schema: type: integer - name: X-Tenant in: header required: true description: >- Tenant identifier. Send the Tenant ID in the `X-Tenant` header to scope API requests to a specific tenant. schema: type: number requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SalePaymentRequest' responses: '200': description: '' content: application/json: schema: type: object properties: success: type: string data: type: object properties: sale_id: type: string remaining_balance: type: string transaction: type: object properties: id: type: - string - 'null' type: type: - string - 'null' credit: type: - string - 'null' debit: type: - string - 'null' currency_id: type: - string - 'null' exchange_rate: type: - string - 'null' invoice_number: type: - string - 'null' description: type: - string - 'null' is_installment: type: boolean installment_number: type: - string - 'null' total_installments: type: - string - 'null' due_date: type: - string - 'null' required: - id - type - credit - debit - currency_id - exchange_rate - invoice_number - description - is_installment - installment_number - total_installments - due_date required: - sale_id - remaining_balance - transaction required: - success - data '401': $ref: '#/components/responses/AuthenticationException' '403': $ref: '#/components/responses/AuthorizationException' '404': description: '' content: application/json: schema: type: object properties: success: type: boolean error_code: type: string const: RESOURCE_NOT_FOUND message: type: string errors: type: 'null' data: type: 'null' required: - success - error_code - message - errors - data '409': $ref: '#/components/responses/CustomerErasedException' '422': $ref: '#/components/responses/ValidationException' '428': description: >- Mandatory setup is incomplete. Finish the setup wizard first; `data.next_step` names the step to continue with. content: application/json: schema: type: object properties: success: type: boolean examples: - false error_code: type: string enum: - SETUP_REQUIRED examples: - SETUP_REQUIRED message: type: string examples: - Complete the required setup steps to continue. data: type: object properties: next_step: type: - string - 'null' examples: - clinic_info required: - next_step required: - success - error_code - message - data components: schemas: SalePaymentRequest: type: object properties: amount: type: number description: Monetary amount. minimum: 0.01 currency_id: type: - integer - 'null' description: Currency of the payment; defaults to the sale currency. exchange_rate: type: - number - 'null' description: Currency exchange rate. minimum: 0 transaction_date: type: - string - 'null' format: date-time description: Transaction date (YYYY-MM-DD). type: type: - string - 'null' description: The transaction type; defaults to a collection when omitted. enum: - collection - payment - null payment_method: $ref: '#/components/schemas/PaymentMethod' description: The payment method used for this collection or payment. invoice_number: type: - string - 'null' description: The invoice number the payment belongs to. maxLength: 255 description: type: - string - 'null' description: The description. maxLength: 65535 installment_number: type: - integer - 'null' description: >- The installment (1-based) of an installment sale this collection settles. Must exist in the sale's installment plan, and the collections linked to one installment cannot exceed its amount. Not allowed for payments. minimum: 1 account_id: type: - integer - 'null' description: Account ID. required: - amount - payment_method title: SalePaymentRequest PaymentMethod: type: string enum: - bank_account - cash - transfer_cash - other - clinic_credit_card - credit_card - private_insurance - sgk title: PaymentMethod responses: AuthenticationException: description: Unauthenticated content: application/json: schema: type: object properties: message: type: string description: Error overview. required: - message AuthorizationException: description: Authorization error content: application/json: schema: type: object properties: message: type: string description: Error overview. required: - message CustomerErasedException: description: The patient record has been erased and is read-only content: application/json: schema: type: object properties: success: type: boolean description: Always false for an error. examples: - false error_code: type: string description: Machine-readable error code. examples: - CUSTOMER_ERASED message: type: string description: Localized error message. required: - success - error_code - message ValidationException: description: Validation error content: application/json: schema: type: object properties: message: type: string description: Errors overview. errors: type: object description: A detailed description of each field that failed validation. additionalProperties: type: array items: type: string required: - message - errors securitySchemes: oauth2: type: oauth2 flows: authorizationCode: authorizationUrl: https://dev.flextell.ai/oauth/authorize tokenUrl: https://dev.flextell.ai/oauth/token scopes: '*': all bearer: type: http scheme: bearer ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.