Retail Pay (Merchant Scans User QR)

Retail Pay is a merchant-initiated payment flow in which the merchant scans a dynamic code displayed by the user inside the Rebell SuperApp. The merchant backend uses the scanned paymentAuthCode to create and authorize a payment request through Rebell’s Payment API. This flow is designed for in-store payments, POS systems, kiosks, and any physical checkout environment where the merchant initiates the transaction.

When to Use Retail Pay

Best For
Not Suitable For

Ideal use cases:

In-store POS systems with barcode scanners
Mobile POS applications
Self-service kiosks
Physical checkout counters
Fast, real-time authorization flows
Alipay/WeChat “scan-to-pay” style experience

Payment Flow

User Displays Code

Customer opens the Rebell SuperApp and displays their dynamic payment code (QR or barcode)

Merchant Scans

Merchant POS or terminal scans the code to capture the paymentAuthCode

API Call

Merchant backend receives the paymentAuthCode and calls Rebell’s Retail Pay API

Process Payment

Rebell processes the payment and returns:

SUCCESS (final)
PROCESSING (requires polling)
FAIL (rejected or invalid code)

Webhook Notification

Rebell sends a webhook notification with the final payment result

Complete Transaction

Merchant backend updates the POS and completes the sale

Sequence Diagram

API Specification

Endpoint

POST /v1/payments/retailPay

Request Headers

Include standard authentication headers:

Client-Id: your-client-id
Request-Time: 2024-01-10T12:22:30Z
Signature: algorithm=SHA256withRSA, keyVersion=1, signature=...
Content-Type: application/json

Request Body

productCode

string

required

Payment product type assigned by Rebell

paymentRequestId

string

required

Merchant-generated unique ID (idempotency key). Must be unique per transaction.

paymentAuthCode

string

required

Dynamic code scanned from the user’s app

paymentAmount

object

required

Payment amount details

Show properties

currency

string

required

Always “EUR”

value

integer

required

Amount in minor units (e.g., 1250 → €12.50)

order

object

Order details

Show properties

orderDescription

string

Description shown on merchant receipt

merchant.store.externalStoreId

string

Useful for multi-store setups

Example Request:

{
  "productCode": "51051000101000100040",
  "paymentRequestId": "pos-20240321-0001",
  "paymentAuthCode": "281012020262467128",
  "paymentAmount": {
    "currency": "EUR",
    "value": 1250
  },
  "order": {
    "orderDescription": "Cappuccino and croissant",
    "merchant": {
      "store": {
        "externalStoreId": "STORE-001"
      }
    }
  }
}

Response Parameters

result

object

required

Payment result details

Show properties

resultCode

string

Result code (SUCCESS, PROCESSING, PAYMENT_FAIL, etc.)

resultStatus

string

Status indicator: “S” (success), “U” (unknown/processing), “F” (fail)

resultMessage

string

Human-readable error message (only present on failure)

paymentId

string

Rebell’s unique payment identifier (present on SUCCESS or PROCESSING)

Response Examples:

{
  "result": {
    "resultCode": "SUCCESS",
    "resultStatus": "S"
  },
  "paymentId": "20240321000123456789"
}

Handling Response Status

When Rebell Returns SUCCESS

Payment is authorized and final

Payment is complete and settled
You may immediately print receipt and deliver goods
No need to wait for webhook (though you’ll still receive one)

When Rebell Returns PROCESSING

Payment is pending - action requiredMerchant MUST:

Start polling inquiryPayment API every 3-5 seconds
Continue polling for up to 30 seconds or until webhook is received
Treat the payment as PENDING until resolved
Display “Awaiting confirmation…” message on POS

Example Polling Logic

async function handleProcessingPayment(paymentId) {
  const maxAttempts = 10; // 30 seconds with 3-second intervals
  let attempts = 0;

  while (attempts < maxAttempts) {
    await new Promise(resolve => setTimeout(resolve, 3000)); // Wait 3 seconds

    const status = await inquiryPayment(paymentId);

    if (status.resultStatus === 'S') {
      return 'SUCCESS';
    } else if (status.resultStatus === 'F') {
      return 'FAILED';
    }

    attempts++;
  }

  return 'TIMEOUT'; // Webhook will provide final status
}

When Rebell Returns FAIL

Error Scenarios & Recovery

Invalid or Expired Payment Code

ResultCode: INVALID_CODECause: The scanned paymentAuthCode is invalid or expiredRecovery:

Ask the user to refresh their payment code in the SuperApp
Retry by scanning the new code
Payment codes typically expire after 60 seconds

Risk Review Required

ResultCode: NEED_RISK_CHALLENGECause: Rebell requires additional risk verificationRecovery:

Display on POS: “Please confirm the payment in your app”
Wait for webhook notification or poll inquiry API
User must approve payment in their SuperApp

User Rejected Payment

ResultCode: PAYMENT_REJECTEDCause: User explicitly denied the transaction in the appRecovery:

Inform customer that payment was declined
Request alternative payment method
Do not retry automatically

Timeout / Connection Issues

Cause: Network error or timeout during API callRecovery:

Retry the request (safe due to paymentRequestId idempotency)
Never create a new paymentRequestId for the same transaction
If retries fail, wait for webhook notification

Security Considerations

Critical Security Requirements:

✅ Always use HTTPS between POS → backend and backend → Rebell
✅ Never expose paymentAuthCode in logs publicly
✅ Use short paymentRequestId TTLs in your database
✅ Validate webhook signatures (see Webhooks)
✅ Implement fraud checks (store/device mapping, rate limits)
✅ Ensure POS devices are in secure environments

Best Practices

Store paymentAuthCode only temporarily during transaction
Log transaction attempts without exposing sensitive codes
Implement device authentication for POS terminals
Monitor for unusual scanning patterns or high failure rates
Set transaction amount limits per merchant policy

UX Recommendations

Create a smooth checkout experience:

Visual Confirmation

POS should visually confirm when scanning succeeded with clear feedback

Processing Indicator

If PROCESSING, show a spinner with “Awaiting confirmation…” message

Error Messages

Display clear, actionable error messages when codes are expired or unreadable

Timeout Handling

Avoid blocking the cashier longer than 30-40 seconds. Offer alternatives.

Optional enhancements:

Sound/vibration feedback when payment succeeds
Automatic receipt printing on success
Display payment amount before scanning for verification

Testing Checklist

Before going live, test these scenarios in sandbox:

Next Steps

Inquiring Payment API

Learn how to poll payment status for PROCESSING transactions

Webhooks

Implement webhook handlers for final payment notifications

Error Handling

Complete reference for error codes and recovery strategies

QR Order Pay

Alternative flow where user scans merchant’s QR code

Getting started

Quick Start

Payment Integration

Mini App Development

When to Use Retail Pay

Payment Flow

Sequence Diagram

API Specification

Endpoint

Request Headers

Request Body

Response Parameters

Handling Response Status

When Rebell Returns SUCCESS

When Rebell Returns PROCESSING

When Rebell Returns FAIL

Error Scenarios & Recovery

Security Considerations

Best Practices

UX Recommendations

Visual Confirmation

Processing Indicator

Error Messages

Timeout Handling

Testing Checklist

Next Steps

Inquiring Payment API

Webhooks

Error Handling

QR Order Pay

Getting started

Quick Start

Payment Integration

Mini App Development

​When to Use Retail Pay

​Payment Flow

​Sequence Diagram

​API Specification

​Endpoint

​Request Headers

​Request Body

​Response Parameters

​Handling Response Status

​When Rebell Returns SUCCESS

​When Rebell Returns PROCESSING

​When Rebell Returns FAIL

​Error Scenarios & Recovery

​Security Considerations

​Best Practices

​UX Recommendations

Visual Confirmation

Processing Indicator

Error Messages

Timeout Handling

​Testing Checklist

​Next Steps

Inquiring Payment API

Webhooks

Error Handling

QR Order Pay

When to Use Retail Pay

Payment Flow

Sequence Diagram

API Specification

Endpoint

Request Headers

Request Body

Response Parameters

Handling Response Status

When Rebell Returns SUCCESS

When Rebell Returns PROCESSING

When Rebell Returns FAIL

Error Scenarios & Recovery

Security Considerations

Best Practices

UX Recommendations

Testing Checklist

Next Steps