openapi: 3.1.0
info:
  title: Paytm Payment Gateway Payments API
  description: Server-to-server REST APIs for Paytm Payment Gateway integrations. Covers transaction initiation (returning a txnToken used by checkout SDKs), transaction processing for selected payment modes, and refund initiation. Requests are signed via Paytm's checksum logic and the signature is sent in the request head.
  version: '1.0'
  contact:
    name: Paytm for Business
    url: https://business.paytm.com/docs/api/
servers:
- url: https://securegw.paytm.in
  description: Production
- url: https://securegw-stage.paytm.in
  description: Staging
- url: https://secure.paytmpayments.com
  description: Production (paytmpayments.com host)
- url: https://securestage.paytmpayments.com
  description: Staging (paytmpayments.com host)
security: []
tags:
- name: Payments
paths:
  /theia/api/v1/initiateTransaction:
    post:
      tags:
      - Payments
      summary: Initiate transaction
      description: Creates a transaction at Paytm and returns a txnToken (valid 15 minutes) that the merchant uses to invoke the checkout SDK or call processTransaction.
      operationId: initiateTransaction
      parameters:
      - name: mid
        in: query
        required: true
        schema:
          type: string
        description: Merchant ID issued by Paytm.
      - name: orderId
        in: query
        required: true
        schema:
          type: string
        description: Merchant-generated unique order id (max 50 chars).
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                head:
                  type: object
                  properties:
                    signature:
                      type: string
                      description: Checksum generated from the request body.
                body:
                  type: object
                  properties:
                    requestType:
                      type: string
                      example: Payment
                    mid:
                      type: string
                    orderId:
                      type: string
                    txnAmount:
                      type: object
                      properties:
                        value:
                          type: string
                        currency:
                          type: string
                          example: INR
                    userInfo:
                      type: object
                      properties:
                        custId:
                          type: string
                    websiteName:
                      type: string
                    callbackUrl:
                      type: string
      responses:
        '200':
          description: Transaction initiated; response contains body.txnToken.
  /theia/api/v1/processTransaction:
    post:
      tags:
      - Payments
      summary: Process transaction
      description: Processes a transaction for the selected payment mode. Requires the txnToken from initiateTransaction in the request header.
      operationId: processTransaction
      parameters:
      - name: mid
        in: query
        required: true
        schema:
          type: string
      - name: orderId
        in: query
        required: true
        schema:
          type: string
      - name: txnToken
        in: header
        required: true
        schema:
          type: string
        description: 15-minute-lived txnToken from initiateTransaction.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                head:
                  type: object
                  properties:
                    signature:
                      type: string
                body:
                  type: object
                  properties:
                    mid:
                      type: string
                    orderId:
                      type: string
                    paymentMode:
                      type: string
                      description: BALANCE, CREDIT_CARD, DEBIT_CARD, NET_BANKING, UPI, etc.
      responses:
        '200':
          description: Returns either a redirect/bank form or an immediate payment result.
components:
  securitySchemes:
    paytmChecksum:
      type: apiKey
      in: header
      name: signature
      description: Checksum signature computed over the request body using Paytm's merchant key. Carried in the request head.signature property and/or as a request header per endpoint guidance.