Affirm Transactions API

openapi: 3.1.0
info:
  title: Affirm Checkout Authorization Transactions API
  description: The Affirm Checkout API enables merchants to initiate and manage the Affirm buy now pay later checkout flow for customers at the point of purchase. It provides endpoints to create and store checkout sessions, read and update checkout objects, and resend checkout links via email or SMS. The API supports both redirect and direct checkout integration patterns. Once a customer authorizes a loan, the resulting checkout token is exchanged server-side to complete the transaction authorization via the Transactions API. Authentication uses HTTP Basic Authentication with the merchant's public and private API keys.
  version: '1.0'
  contact:
    name: Affirm Developer Support
    url: https://docs.affirm.com/developers/docs/development-quickstart
  termsOfService: https://www.affirm.com/legal/merchant-terms
servers:
- url: https://api.affirm.com/api/v1
  description: Production Server
- url: https://sandbox.affirm.com/api/v1
  description: Sandbox Server
security:
- basicAuth: []
tags:
- name: Transactions
  description: Post-authorization transaction management operations including capture, void, and refund.
paths:
  /transactions/{id}/capture:
    post:
      operationId: captureDirectTransaction
      summary: Affirm Capture a Transaction
      description: Captures a previously authorized transaction to initiate transfer of funds to the merchant. Capture may be for the full authorized amount or a partial amount when split capture is in use. The merchant should capture only upon order fulfillment or shipment to align with Affirm's terms of service.
      tags:
      - Transactions
      parameters:
      - $ref: '#/components/parameters/TransactionId'
      requestBody:
        required: false
        content:
          application/json:
            schema:
              type: object
              properties:
                amount:
                  type: integer
                  description: Amount to capture in cents. Defaults to the full authorized amount.
                order_id:
                  type: string
                  description: Merchant order identifier for this capture event.
                shipping_carrier:
                  type: string
                  description: Name of the shipping carrier for this fulfillment.
                shipping_confirmation:
                  type: string
                  description: Tracking number or shipment confirmation.
            examples:
              captureDirectTransactionRequestExample:
                summary: Default captureDirectTransaction request
                x-microcks-default: true
                value:
                  amount: 1
                  order_id: '500123'
                  shipping_carrier: example_value
                  shipping_confirmation: example_value
      responses:
        '200':
          description: Transaction captured successfully.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Transaction'
              examples:
                captureDirectTransaction200Example:
                  summary: Default captureDirectTransaction 200 response
                  x-microcks-default: true
                  value:
                    id: '500123'
                    checkout_id: '500123'
                    order_id: '500123'
                    status: authorized
                    amount: 1
                    amount_refunded: 1
                    currency: USD
                    created: '2025-03-15T14:30:00Z'
                    authorization_expiration: '2025-03-15T14:30:00Z'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':
          $ref: '#/components/responses/NotFound'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
  /transactions/{id}/void:
    post:
      operationId: voidDirectTransaction
      summary: Affirm Void a Transaction
      description: Voids an authorized but uncaptured transaction, releasing the hold on the customer's Affirm credit. Used when an order is cancelled prior to fulfillment. A voided transaction cannot be captured or refunded.
      tags:
      - Transactions
      parameters:
      - $ref: '#/components/parameters/TransactionId'
      responses:
        '200':
          description: Transaction voided successfully.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Transaction'
              examples:
                voidDirectTransaction200Example:
                  summary: Default voidDirectTransaction 200 response
                  x-microcks-default: true
                  value:
                    id: '500123'
                    checkout_id: '500123'
                    order_id: '500123'
                    status: authorized
                    amount: 1
                    amount_refunded: 1
                    currency: USD
                    created: '2025-03-15T14:30:00Z'
                    authorization_expiration: '2025-03-15T14:30:00Z'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':
          $ref: '#/components/responses/NotFound'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
  /transactions/{id}/refund:
    post:
      operationId: refundDirectTransaction
      summary: Affirm Refund a Transaction
      description: Issues a full or partial refund on a captured Direct API transaction. Partial refunds can be applied multiple times until the total refunded amount equals the captured amount. The customer's Affirm account is credited and the merchant's settlement is adjusted.
      tags:
      - Transactions
      parameters:
      - $ref: '#/components/parameters/TransactionId'
      requestBody:
        required: false
        content:
          application/json:
            schema:
              type: object
              properties:
                amount:
                  type: integer
                  description: Amount to refund in cents. Defaults to the full captured amount.
            examples:
              refundDirectTransactionRequestExample:
                summary: Default refundDirectTransaction request
                x-microcks-default: true
                value:
                  amount: 1
      responses:
        '200':
          description: Transaction refunded successfully.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Transaction'
              examples:
                refundDirectTransaction200Example:
                  summary: Default refundDirectTransaction 200 response
                  x-microcks-default: true
                  value:
                    id: '500123'
                    checkout_id: '500123'
                    order_id: '500123'
                    status: authorized
                    amount: 1
                    amount_refunded: 1
                    currency: USD
                    created: '2025-03-15T14:30:00Z'
                    authorization_expiration: '2025-03-15T14:30:00Z'
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':
          $ref: '#/components/responses/NotFound'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
  /transactions:
    get:
      operationId: listTransactions
      summary: Affirm List Transactions
      description: Returns a paginated list of all transactions for the authenticated merchant. Transactions represent authorized Affirm loans that can be captured, refunded, or voided. Results are sorted by creation date in descending order.
      tags:
      - Transactions
      parameters:
      - $ref: '#/components/parameters/PageLimit'
      - $ref: '#/components/parameters/PageCursor'
      responses:
        '200':
          description: A list of transaction objects.
          content:
            application/json:
              schema:
                type: object
                properties:
                  data:
                    type: array
                    items:
                      $ref: '#/components/schemas/Transaction_2'
                  total:
                    type: integer
                    description: Total number of transactions matching the query.
                  next_cursor:
                    type: string
                    description: Cursor token for fetching the next page of results.
              examples:
                listTransactions200Example:
                  summary: Default listTransactions 200 response
                  x-microcks-default: true
                  value:
                    data:
                    - id: {}
                      checkout_id: {}
                      order_id: {}
                      status: {}
                      amount: {}
                      amount_refunded: {}
                      currency: {}
                      created: {}
                      authorization_expiration: {}
                      provider_id: {}
                      remove_tax: {}
                      events: {}
                      token: {}
                    total: 1
                    next_cursor: example_value
        '401':
          $ref: '#/components/responses/Unauthorized'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
    post:
      operationId: authorizeTransaction
      summary: Affirm Authorize a Transaction
      description: Authorizes a new transaction using a checkout token obtained after a customer completes the Affirm checkout flow. The checkout token is a one-time-use token that must be exchanged server-side within the authorization window. A successful authorization places a hold on the customer's Affirm credit and returns a transaction object with status "authorized". The transaction must subsequently be captured to initiate transfer of funds to the merchant.
      tags:
      - Transactions
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - checkout_token
              properties:
                checkout_token:
                  type: string
                  description: The one-time-use checkout token returned by the Affirm checkout flow after customer authorization.
                order_id:
                  type: string
                  description: The merchant's internal order identifier to associate with this transaction for reconciliation.
            examples:
              authorizeTransactionRequestExample:
                summary: Default authorizeTransaction request
                x-microcks-default: true
                value:
                  checkout_token: abc123def456abc123def456abc123de
                  order_id: '500123'
      responses:
        '200':
          description: Transaction successfully authorized.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Transaction_2'
              examples:
                authorizeTransaction200Example:
                  summary: Default authorizeTransaction 200 response
                  x-microcks-default: true
                  value:
                    id: '500123'
                    checkout_id: '500123'
                    order_id: '500123'
                    status: authorized
                    amount: 1
                    amount_refunded: 1
                    currency: USD
                    created: '2025-03-15T14:30:00Z'
                    authorization_expiration: '2025-03-15T14:30:00Z'
                    provider_id: 1
                    remove_tax: true
                    events:
                    - {}
                    token: abc123def456abc123def456abc123de
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
  /transactions/{id}:
    get:
      operationId: readTransaction
      summary: Affirm Read a Transaction
      description: Retrieves the full details of a specific transaction by its unique identifier. Returns the transaction object including current status, amounts, associated events, order metadata, and authorization expiration time.
      tags:
      - Transactions
      parameters:
      - $ref: '#/components/parameters/TransactionId'
      responses:
        '200':
          description: Transaction object retrieved successfully.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Transaction_2'
              examples:
                readTransaction200Example:
                  summary: Default readTransaction 200 response
                  x-microcks-default: true
                  value:
                    id: '500123'
                    checkout_id: '500123'
                    order_id: '500123'
                    status: authorized
                    amount: 1
                    amount_refunded: 1
                    currency: USD
                    created: '2025-03-15T14:30:00Z'
                    authorization_expiration: '2025-03-15T14:30:00Z'
                    provider_id: 1
                    remove_tax: true
                    events:
                    - {}
                    token: abc123def456abc123def456abc123de
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':
          $ref: '#/components/responses/NotFound'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
    post:
      operationId: updateTransaction
      summary: Affirm Update a Transaction
      description: Updates mutable fields on an existing transaction, such as the merchant order ID. Only fields included in the request body are updated; omitted fields remain unchanged.
      tags:
      - Transactions
      parameters:
      - $ref: '#/components/parameters/TransactionId'
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                order_id:
                  type: string
                  description: Updated merchant order identifier to associate with this transaction.
            examples:
              updateTransactionRequestExample:
                summary: Default updateTransaction request
                x-microcks-default: true
                value:
                  order_id: '500123'
      responses:
        '200':
          description: Transaction updated successfully.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Transaction_2'
              examples:
                updateTransaction200Example:
                  summary: Default updateTransaction 200 response
                  x-microcks-default: true
                  value:
                    id: '500123'
                    checkout_id: '500123'
                    order_id: '500123'
                    status: authorized
                    amount: 1
                    amount_refunded: 1
                    currency: USD
                    created: '2025-03-15T14:30:00Z'
                    authorization_expiration: '2025-03-15T14:30:00Z'
                    provider_id: 1
                    remove_tax: true
                    events:
                    - {}
                    token: abc123def456abc123def456abc123de
        '400':
          $ref: '#/components/responses/BadRequest'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '404':
          $ref: '#/components/responses/NotFound'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
components:
  parameters:
    PageLimit:
      name: limit
      in: query
      required: false
      description: Maximum number of records to return per page.
      schema:
        type: integer
        minimum: 1
        maximum: 100
        default: 20
    TransactionId:
      name: id
      in: path
      required: true
      description: The unique identifier of the transaction.
      schema:
        type: string
    PageCursor:
      name: cursor
      in: query
      required: false
      description: Pagination cursor returned from a previous list response.
      schema:
        type: string
  responses:
    Unauthorized:
      description: Unauthorized. Authentication credentials are missing or invalid.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    BadRequest:
      description: Bad request. The request body or parameters are invalid.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    NotFound:
      description: Not found. The requested resource does not exist.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  schemas:
    Transaction:
      type: object
      description: Represents an Affirm payment transaction at any point in its lifecycle.
      properties:
        id:
          type: string
          description: Unique identifier for this transaction.
          example: '500123'
        checkout_id:
          type: string
          description: Identifier of the checkout session that originated this transaction.
          example: '500123'
        order_id:
          type: string
          description: Merchant's internal order identifier.
          example: '500123'
        status:
          type: string
          description: Current lifecycle status of the transaction.
          enum:
          - authorized
          - captured
          - voided
          - refunded
          - partially_refunded
          example: authorized
        amount:
          type: integer
          description: Original authorized amount in cents.
          example: 1
        amount_refunded:
          type: integer
          description: Cumulative amount refunded in cents.
          example: 1
        currency:
          type: string
          description: ISO 4217 currency code.
          example: USD
        created:
          type: string
          format: date-time
          description: Creation timestamp in RFC 3339 format.
          example: '2025-03-15T14:30:00Z'
        authorization_expiration:
          type: string
          format: date-time
          description: Timestamp after which the authorization can no longer be captured.
          example: '2025-03-15T14:30:00Z'
    Transaction_2:
      type: object
      description: Represents an Affirm payment transaction, capturing the full lifecycle from authorization through capture, refund, and void operations.
      properties:
        id:
          type: string
          description: A unique identifier representing the transaction.
          example: '500123'
        checkout_id:
          type: string
          description: A unique identifier referencing the Checkout object that originated this transaction.
          example: '500123'
        order_id:
          type: string
          description: Identifies the order within the merchant's order management system.
          example: '500123'
        status:
          type: string
          description: Current state of the transaction.
          enum:
          - authorized
          - captured
          - voided
          - refunded
          - partially_refunded
          example: authorized
        amount:
          type: integer
          description: The original amount financed to the customer in this transaction, expressed in the smallest currency unit (e.g., cents for USD).
          example: 1
        amount_refunded:
          type: integer
          description: The cumulative amount refunded back to the customer from this transaction, expressed in the smallest currency unit.
          example: 1
        currency:
          type: string
          description: Local transaction currency following ISO 4217 standards.
          example: USD
        created:
          type: string
          format: date-time
          description: The time when the transaction was created, in RFC 3339 format.
          example: '2025-03-15T14:30:00Z'
        authorization_expiration:
          type: string
          format: date-time
          description: The time when the transaction authorization expires and can no longer be captured, in RFC 3339 format.
          example: '2025-03-15T14:30:00Z'
        provider_id:
          type: integer
          description: A unique identifier of the provider financing the transaction.
          example: 1
        remove_tax:
          type: boolean
          description: Indicates whether tax was paid by the provider (applicable to Affirm Connect only).
          example: true
        events:
          type: array
          description: Array of TransactionEvent objects documenting the transaction history.
          items:
            $ref: '#/components/schemas/TransactionEvent'
          example:
          - example_value
        token:
          type: string
          description: A JWT signing the JSON response. If PII is included, this token is also encrypted.
          example: abc123def456abc123def456abc123de
    Error:
      type: object
      description: Standard error response returned by the Affirm API.
      properties:
        status_code:
          type: integer
          description: HTTP status code of the error.
          example: 1
        code:
          type: string
          description: Machine-readable error code string.
          example: example_value
        message:
          type: string
          description: Human-readable description of the error.
          example: example_value
    TransactionEvent:
      type: object
      description: Represents a single event in the lifecycle of a transaction, such as an authorization, capture, refund, or void.
      properties:
        id:
          type: string
          description: A unique identifier for the transaction event.
          example: '500123'
        type:
          type: string
          description: The type of transaction event.
          enum:
          - auth
          - capture
          - refund
          - void
          - update
          example: auth
        amount:
          type: integer
          description: The amount associated with this event in the smallest currency unit.
          example: 1
        currency:
          type: string
          description: The ISO 4217 currency code for this event.
          example: USD
        fee:
          type: integer
          description: The fee charged by Affirm for this event in the smallest currency unit.
          example: 1
        created:
          type: string
          format: date-time
          description: The time when this event was created, in RFC 3339 format.
          example: '2025-03-15T14:30:00Z'
        reference_id:
          type: string
          description: An external reference identifier associated with this event.
          example: '500123'
        metadata:
          type: object
          description: Additional key-value metadata associated with this event for merchant tracking purposes.
          additionalProperties:
            type: string
          example: {}
  securitySchemes:
    basicAuth:
      type: http
      scheme: basic
      description: HTTP Basic Authentication using the merchant's public API key as the username and private API key as the password, Base64-encoded as per RFC 7617.
externalDocs:
  description: Affirm Checkout API Reference
  url: https://docs.affirm.com/developers/reference/the-checkout-object