> ## Documentation Index > Fetch the complete documentation index at: https://docs.cryptoprocessing.com/llms.txt > Use this file to discover all available pages before exploring further. # Exchange at a fixed rate > Execute an exchange using a valid fixed quote from [/exchange/calculate](/api-reference/endpoints/exchange-calculate). Execute a fixed exchange using a valid quote from [/exchange/calculate](/api-reference/endpoints/exchange-calculate). The exchange request must be sent before the quote expires and must use the same amount and price as in the quote. ## OpenAPI ````yaml POST /exchange/fixed openapi: 3.0.0 info: title: Merchant Backend V2 version: '1.0' description: Documentation for merchant backend processing endpoints servers: - url: https://app.cryptoprocessing.com/api/v2 security: - xProcessingKey: [] tags: - name: Status - name: Balance - name: Currencies - name: Deposit addresses - name: Withdrawal - name: Exchange - name: Invoices - name: Transactions paths: /exchange/fixed: post: tags: - Exchange summary: Exchange at a fixed exchange rate description: >- Execute an exchange using a valid fixed quote from [/exchange/calculate](/api-reference/endpoints/exchange-calculate). operationId: post-exchange-fixed parameters: - $ref: '#/components/parameters/XProcessingSignatureHeader' requestBody: content: application/json: schema: type: object properties: sender_currency: type: string description: >- Currency to exchange from. For a list of all available currencies, see [API currency codes](/api-reference/currency-codes). receiver_currency: type: string description: >- Currency to exchange to. For a list of all available currencies, see [API currency codes](/api-reference/currency-codes). sender_amount: type: number description: >- Amount to send. You must include either this parameter or `receiver_amount`. This value must match the quote returned by `/exchange/calculate`. receiver_amount: type: number description: >- Amount to receive. You must include either this parameter or `sender_amount`. This value must match the quote returned by `/exchange/calculate`. foreign_id: type: string description: Unique ID of the exchange transaction. price: type: number description: >- The quoted exchange rate from `/exchange/calculate`, expressed as units of `receiver_currency` for 1 unit of `sender_currency`. This value must match the quote. required: - sender_currency - receiver_currency - foreign_id - price examples: sender_amount: value: sender_currency: BTC receiver_currency: EUR sender_amount: 0.003 foreign_id: test_foreign_id_0250 price: '77314.26444333' receiver_amount: value: sender_currency: BTC receiver_currency: EUR receiver_amount: 100 foreign_id: test_foreign_id_0310 price: 77314.40676655 responses: '201': description: Created content: application/json: schema: type: object properties: data: type: object required: - id - foreign_id - type - sender_amount - sender_currency - receiver_amount - receiver_currency - fee_amount - fee_currency - price - status properties: id: type: integer description: Transaction ID. foreign_id: type: string description: This exchange's unique identifier in your system. type: type: string description: Transaction type. sender_amount: type: string description: The amount being exchanged. sender_currency: type: string description: The currency being exchanged from. receiver_amount: type: string description: The amount to be received. receiver_currency: type: string description: The currency being exchanged to. fee_amount: type: string description: >- The exchange fee amount. If the fee is charged in the sender currency, the total debited amount is `sender_amount + fee_amount`. fee_currency: type: string description: The currency in which the exchange fee is charged. price: type: string description: >- The quoted exchange rate from `/exchange/calculate`, expressed as units of `receiver_currency` for 1 unit of `sender_currency`. status: type: string description: Exchange status. examples: sender_amount: value: data: sender_currency: BTC sender_amount: '0.00300000' receiver_currency: EUR receiver_amount: '231.94279333' fee_currency: BTC fee_amount: '0.00015000' price: '77314.26444333' id: 134704049 foreign_id: test_foreign_id_0250 type: exchange status: processing receiver_amount: value: data: sender_currency: BTC sender_amount: '0.00129342' receiver_currency: EUR receiver_amount: '100.00000000' fee_currency: BTC fee_amount: '0.00006467' price: '77314.40676655' id: 134704197 foreign_id: test_foreign_id_0310 type: exchange status: processing '400': description: Bad Request. content: application/json: schema: $ref: '#/components/schemas/ValidationOrMalformedJson' examples: Rate expired: summary: Fixed rate has expired value: errors: message: Fix time is up. Exchange price is changed. Insufficient balance: summary: Not enough balance for exchange value: errors: sender_amount: 'Insufficient balance. Available: 0.00500000 BTC' Invalid sender currency: summary: Sender currency not supported value: errors: sender_currency: Currency not supported Invalid receiver currency: summary: Receiver currency not supported value: errors: receiver_currency: Currency not supported Invalid amount: summary: Amount below minimum or invalid value: errors: sender_amount: The amount must be at least 0.00010000 BTC Missing foreign_id: summary: Foreign ID missing value: errors: foreign_id: The foreign_id field is required Malformed JSON: summary: Invalid JSON body value: error: Bad content format code: bad_content_format '403': $ref: '#/components/responses/HeaderAuthorization' components: parameters: XProcessingSignatureHeader: name: X-Processing-Signature in: header required: true description: >- Hex-encoded HMAC-SHA512 signature of the request body, [generated using your secret key](/api-reference/authentication). schema: type: string schemas: ValidationOrMalformedJson: oneOf: - type: object title: ValidationError description: One or more request parameters failed validation. properties: errors: type: object additionalProperties: type: string - type: object title: MalformedJson description: >- The request body is not valid JSON or the Content-Type header is not set to `application/json`. properties: error: type: string code: type: string responses: HeaderAuthorization: description: | Forbidden content: application/json: schema: type: object properties: error: type: string description: Human-readable error message. code: type: string description: Error code. description: >- Invalid or missing headers. Refer to [Errors](/api-reference/errors#403) for troubleshooting steps. examples: Bad signature header: value: error: Bad signature header code: bad_header_signature No signature header: value: error: No signature header code: required_header_signature Bad key header: value: error: Bad key header code: bad_header_key No key header: value: error: No key header code: required_header_key securitySchemes: xProcessingKey: type: apiKey description: Your [API key](/integration-guide/get-your-api-key). in: header name: X-Processing-Key ````