Flex Refund API Guide - Flex Documentation

Important IDs to store:

checkout_session_id - Extract from redirect URL (e.g., fcs_01kbjcmbt5mhsmaggfqc1a4rns)
This ID is required for creating refunds

You can also retrieve the checkout session to get additional details:

GET /v1/checkout/sessions/{checkout_session_id}

Response includes:

payment_intent_id - Flex’s internal payment ID
latest_charge - Charge ID
status - Should be complete for refunds

Primary Refund Endpoint

POST /v1/checkout/sessions//refund

This is the main refund endpoint for processing refunds on completed checkout sessions. Base URL: https://api.withflex.com (or your custom domain) Authentication:

Authorization: Bearer YOUR_API_KEY
Content-Type: application/json

Request Format

Option 1: Line Item-Based Refund (Granular Control)

Refund specific products/prices with custom amounts:

{
  "checkout_session": {
    "line_items": [
      {
        "product": "fprod_01k3m6j3zqcvy6pbj1a65sszpw",
        "amount_to_refund": 2000
      },
      {
        "product": "fprod_01k3m6r0qj2bpc25q6h56r3jar",
        "amount_to_refund": 1500
      }
    ],
    "amount_tax": 350,
    "amount_shipping": 500,
    "amount_discount": 200,
    "refund_metadata": {
      "OrderNo": "ORDER123",
      "Source": "Customer_Request",
      "Reason": "Damaged_Product"
    }
  }
}

Alternative: Use price instead of product

{
  "checkout_session": {
    "line_items": [
      {
        "price": "fprice_01k3m6j3zqcvy6pbj1a65sszpw",
        "amount_to_refund": 2000
      }
    ],
    "refund_metadata": {
      "reason": "customer_request"
    }
  }
}

Option 2: Simple Amount-Based Refund

Refund a specific total amount without line item breakdown:

{
  "checkout_session": {
    "amount": 5000,
    "refund_metadata": {
      "reason": "customer_not_satisfied",
      "order_id": "12345"
    }
  }
}

Option 3: Full Refund

Refund the entire checkout session amount:

{
  "checkout_session": {
    "refund_metadata": {
      "reason": "order_cancelled"
    }
  }
}

Or simply:

{
  "checkout_session": {}
}

Request Parameters

Field	Type	Required	Description
`line_items`	array	No	Specific line items to refund with amounts
`line_items[].product`	string	One of	Product ID to refund (e.g., `fprod_xxx`)
`line_items[].price`	string	product/price	Price ID to refund (e.g., `fprice_xxx`)
`line_items[].amount_to_refund`	integer	No	Amount in cents for this item (omit for full item refund)
`amount`	integer	No	Total amount to refund in cents (alternative to line_items)
`amount_tax`	integer	No	Tax amount to refund in cents
`amount_shipping`	integer	No	Shipping amount to refund in cents
`amount_discount`	integer	No	Discount amount to refund in cents
`refund_metadata`	object	No	Key-value pairs for tracking (order ID, reason, etc.)

Success Response

Status Code: 200 OK

{
  "checkout_session": {
    "checkout_session_id": "fcs_01kbjcmbt5mhsmaggfqc1a4rns",
    "status": "complete",
    "amount_total": 10000,
    "amount_subtotal": 9000,
    "currency": "usd",
    "customer": {
      "customer_id": "fcus_xxx",
      "email": "customer@example.com",
      "name": "John Doe"
    },
    "payment_intent": {
      "payment_intent_id": "fpi_xxx",
      "amount": 10000,
      "amount_received": 10000,
      "status": "succeeded"
    },
    "line_items": [...],
    "refunds": [
      {
        "refund_id": "fref_01kbjdxyz123",
        "payment_intent_id": "fpi_xxx",
        "amount": 3500,
        "status": "pending",
        "reason": null,
        "created_at": "2024-12-04T10:30:00Z",
        "test_mode": false,
        "metadata": {
          "OrderNo": "ORDER123",
          "Source": "Customer_Request"
        },
        "reference_id": null,
        "reference_type": "acquirer_reference_number",
        "reference_status": "pending",
        "items": [
          {
            "amount_refunded": 3500,
            "payment_intent": "fpi_xxx",
            "reference_id": null,
            "reference_type": "acquirer_reference_number",
            "reference_status": "pending"
          }
        ]
      }
    ]
  }
}

Key Response Fields:

refunds[].refund_id - Store this for tracking refund status
refunds[].status - Current refund status (pending, succeeded, failed)
refunds[].reference_id - Acquirer Reference Number (ARN) for bank tracking (populated later)
refunds[].reference_status - Status of reference number (pending, available, unavailable)

Error Responses

Checkout Session Not Complete (422 Unprocessable Entity)

{
  "error": {
    "type": "validation_error",
    "message": "Checkout session must be complete",
    "errors": [
      {
        "loc": ["status"],
        "msg": "Checkout session must be complete",
        "type": "invalid_request_error"
      }
    ]
  }
}

Cause: Checkout session status is not complete

Checkout Session Not Found (404 Not Found)

{
  "error": {
    "type": "not_found",
    "message": "checkout session does not exist"
  }
}

Cause: Invalid checkout_session_id or doesn’t belong to your account

Unauthorized (401 Unauthorized)

{
  "error": {
    "type": "unauthorized",
    "message": "Invalid API key"
  }
}

Cause: Missing or invalid Authorization header

Refund Statuses

Status	Description
`pending`	Refund initiated, processing in progress
`requires_action`	Additional action required (rare)
`succeeded`	Refund completed, funds returned to customer
`failed`	Refund failed (usually insufficient funds in connected account)
`canceled`	Refund was canceled

Typical Timeline:

Refund status updates to succeeded within minutes to hours
Funds appear in customer’s account within 5-10 business days (varies by bank)

Reference Numbers for Tracking

Flex provides reference numbers that can be used to track refunds with banks and payment networks.

Reference Types

Type	Description
`acquirer_reference_number`	ARN - Most common, used for tracking with issuing banks
`system_trace_audit_number`	Alternative tracking number for payment networks
`retrieval_reference_number`	Used for dispute resolution and chargebacks

Reference Status

Status	Description
`pending`	Reference number not yet available from payment network
`available`	Reference number ready, can be provided to customer/bank
`unavailable`	Payment network doesn’t provide this reference type

Note: Reference IDs typically become available within hours after the refund is created. Learn More: Stripe Reference Numbers Guide

Complete Workflow Examples

Example 1: Full Refund

Step 1: Customer completes payment You receive redirect after successful payment:

https://yoursite.com/success?session_id=fcs_01kbjcmbt5mhsmaggfqc1a4rns

Step 2: Customer requests full refund

curl -X POST https://api.withflex.com/v1/checkout/sessions/fcs_01kbjcmbt5mhsmaggfqc1a4rns/refund \
  -H "Authorization: Bearer sk_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{
    "checkout_session": {
      "refund_metadata": {
        "reason": "customer_cancelled_order",
        "order_id": "ORD-12345",
        "requested_by": "customer_service"
      }
    }
  }'

Step 3: Response

{
  "checkout_session": {
    "checkout_session_id": "fcs_01kbjcmbt5mhsmaggfqc1a4rns",
    "status": "complete",
    "amount_total": 15000,
    "refunds": [
      {
        "refund_id": "fref_01kbjdxyz123",
        "amount": 15000,
        "status": "pending",
        "created_at": "2024-12-04T10:30:00Z",
        "metadata": {
          "reason": "customer_cancelled_order",
          "order_id": "ORD-12345"
        }
      }
    ]
  }
}

Step 4: Track refund status (optional)

curl -X GET https://api.withflex.com/v1/refunds/fref_01kbjdxyz123 \
  -H "Authorization: Bearer sk_live_xxx"

Example 2: Partial Refund by Line Items

Scenario: Customer returns 1 of 3 items purchased Request:

curl -X POST https://api.withflex.com/v1/checkout/sessions/fcs_01kbjcmbt5mhsmaggfqc1a4rns/refund \
  -H "Authorization: Bearer sk_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{
    "checkout_session": {
      "line_items": [
        {
          "product": "fprod_yoga_mat",
          "amount_to_refund": 3500
        }
      ],
      "amount_tax": 280,
      "amount_shipping": 0,
      "refund_metadata": {
        "reason": "item_returned",
        "rma_number": "RMA-2024-1234",
        "returned_items": "Yoga Mat (Blue)"
      }
    }
  }'

Explanation:

Refunding only the yoga mat: $35.00
Including proportional tax: $2.80
Not refunding shipping (customer kept other items)
Total refund: $37.80

Example 3: Partial Refund by Amount

Scenario: Price adjustment without item-level detail Request:

curl -X POST https://api.withflex.com/v1/checkout/sessions/fcs_01kbjcmbt5mhsmaggfqc1a4rns/refund \
  -H "Authorization: Bearer sk_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{
    "checkout_session": {
      "amount": 2000,
      "refund_metadata": {
        "reason": "price_match_guarantee",
        "original_amount": 15000,
        "adjusted_amount": 13000,
        "competitor": "CompetitorStore"
      }
    }
  }'

Explanation:

Refunding $20.00 difference due to price match
No line item breakdown needed
Metadata tracks the reason

Example 4: Multiple Partial Refunds

You can create multiple refunds for the same checkout session until the full amount is refunded. First refund: $50

curl -X POST https://api.withflex.com/v1/checkout/sessions/fcs_xxx/refund \
  -H "Authorization: Bearer sk_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{"checkout_session": {"amount": 5000}}'

Second refund: $30

curl -X POST https://api.withflex.com/v1/checkout/sessions/fcs_xxx/refund \
  -H "Authorization: Bearer sk_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{"checkout_session": {"amount": 3000}}'

Important: Track the total refunded amount to avoid over-refunding.

Secondary Refund API

Tracking and Listing Refunds

After creating a refund via the checkout session endpoint, use the secondary refund API to track status:

GET /v1/refunds/

curl -X GET https://api.withflex.com/v1/refunds/fref_01kbjdxyz123 \
  -H "Authorization: Bearer sk_live_xxx"

Response:

{
  "refund": {
    "refund_id": "fref_01kbjdxyz123",
    "payment_intent_id": "fpi_xxx",
    "amount": 5000,
    "status": "succeeded",
    "reason": null,
    "created_at": "2024-12-04T10:30:00Z",
    "test_mode": false,
    "metadata": {
      "order_id": "12345"
    },
    "reference_id": "ARN8493274932",
    "reference_type": "acquirer_reference_number",
    "reference_status": "available",
    "items": [...]
  }
}

GET /v1/refunds (List Refunds)

Query Parameters:

payment_intent - Filter by payment intent ID
checkout_session - Filter by checkout session ID
status - Filter by status

Examples:

# All refunds
curl -X GET https://api.withflex.com/v1/refunds \
  -H "Authorization: Bearer sk_live_xxx"

# Refunds for specific checkout session
curl -X GET https://api.withflex.com/v1/refunds?checkout_session=fcs_01kbjcmbt5mhsmaggfqc1a4rns \
  -H "Authorization: Bearer sk_live_xxx"

# Succeeded refunds only
curl -X GET https://api.withflex.com/v1/refunds?status=succeeded \
  -H "Authorization: Bearer sk_live_xxx"

Response:

{
  "refunds": [
    {
      "refund_id": "fref_01kbjdxyz123",
      "payment_intent_id": "fpi_xxx",
      "amount": 5000,
      "status": "succeeded",
      "created_at": "2024-12-04T10:30:00Z",
      ...
    },
    {
      "refund_id": "fref_01kbjdabc456",
      "payment_intent_id": "fpi_yyy",
      "amount": 3000,
      "status": "pending",
      "created_at": "2024-12-03T15:20:00Z",
      ...
    }
  ]
}

PATCH /v1/refunds/ (Update Refund Metadata)

Update refund metadata or reason (does not change amount or status):

curl -X PATCH https://api.withflex.com/v1/refunds/fref_01kbjdxyz123 \
  -H "Authorization: Bearer sk_live_xxx" \
  -H "Content-Type: application/json" \
  -d '{
    "refund": {
      "reason": "fraudulent",
      "metadata": {
        "updated_by": "admin",
        "investigation_id": "INV-2024-001"
      }
    }
  }'

Implementation Details

Automatic Handling by Flex

Flex automatically handles: ✅ Reverse Transfer - Funds are clawed back from the connected account (partner) ✅ Application Fee Retention - Flex keeps the platform fee (not refunded) ✅ Webhook Processing - Status updates via Stripe webhooks ✅ Charge Tracking - Records which charges were refunded in refund_charge table ✅ Reference Number Retrieval - ARN and other tracking numbers populated when available

Partial Refund Behavior

Can refund any amount up to the original charge amount
Multiple partial refunds allowed until full amount refunded
Track amount_received vs total refunded to calculate remaining refundable amount

Tax, Shipping, and Discount Refunds

When refunding line items, you can specify component amounts:

{
  "checkout_session": {
    "line_items": [
      {
        "product": "fprod_xxx",
        "amount_to_refund": 5000
      }
    ],
    "amount_tax": 400,        // Proportional tax for refunded items
    "amount_shipping": 500,    // Shipping refund
    "amount_discount": 250     // Discount adjustment
  }
}

Best Practice: Calculate proportional tax when refunding partial line items.

Best Practices

1. Store Checkout Session ID

Always save the checkout_session_id after payment completion:

// After payment redirect
const urlParams = new URLSearchParams(window.location.search);
const sessionId = urlParams.get('session_id');

// Store in your database
await db.orders.update({
  orderId: orderId,
  flexCheckoutSessionId: sessionId
});

2. Verify Checkout Session Status

Before attempting refund, confirm the session is complete:

const session = await fetch(
  `https://api.withflex.com/v1/checkout/sessions/${sessionId}`,
  {
    headers: {
      'Authorization': `Bearer ${apiKey}`
    }
  }
).then(r => r.json());

if (session.checkout_session.status !== 'complete') {
  throw new Error('Cannot refund incomplete checkout session');
}

3. Use Metadata for Tracking

Always include metadata to track refund context:

{
  "checkout_session": {
    "amount": 5000,
    "refund_metadata": {
      "order_id": "ORD-12345",
      "reason": "customer_request",
      "requested_by": "customer_service_agent_42",
      "ticket_id": "TICKET-789",
      "timestamp": "2024-12-04T10:30:00Z"
    }
  }
}

4. Handle Refund Webhooks

Subscribe to Flex webhooks for automatic refund status updates: Event Types:

refund.created - Refund initiated
refund.succeeded - Refund completed successfully
refund.failed - Refund failed

Webhook Payload Example:

{
  "type": "refund.succeeded",
  "data": {
    "object": {
      "refund_id": "fref_xxx",
      "payment_intent_id": "fpi_xxx",
      "amount": 5000,
      "status": "succeeded",
      "reference_id": "ARN123456789"
    }
  }
}

5. Track Remaining Refundable Amount

For multiple partial refunds, track the remaining amount:

const session = await getCheckoutSession(sessionId);
const totalCharged = session.amount_total;
const totalRefunded = session.refunds.reduce((sum, r) => sum + r.amount, 0);
const remainingRefundable = totalCharged - totalRefunded;

console.log(`Can still refund: $${remainingRefundable / 100}`);

6. Save Reference Numbers

Store ARNs for customer support inquiries:

const refund = await getRefund(refundId);

if (refund.reference_status === 'available') {
  await db.refunds.update({
    refundId: refundId,
    arn: refund.reference_id,
    referenceType: refund.reference_type
  });

  // Provide to customer for bank tracking
  console.log(`ARN: ${refund.reference_id}`);
}

7. Handle Errors Gracefully

try {
  const response = await fetch(refundUrl, {
    method: 'POST',
    headers: { 'Authorization': `Bearer ${apiKey}` },
    body: JSON.stringify(refundRequest)
  });

  if (!response.ok) {
    const error = await response.json();

    if (error.error.type === 'validation_error') {
      console.error('Validation error:', error.error.message);
      // Handle validation errors
    } else if (response.status === 404) {
      console.error('Checkout session not found');
      // Handle not found
    } else {
      console.error('Unexpected error:', error);
      // Handle other errors
    }
  }

  const result = await response.json();
  console.log('Refund created:', result.checkout_session.refunds[0].refund_id);

} catch (error) {
  console.error('Network error:', error);
  // Handle network errors
}

Testing

Test Mode

Use test API keys (starting with sk_test_) to test refunds without affecting real money:

curl -X POST https://api.withflex.com/v1/checkout/sessions/fcs_test_xxx/refund \
  -H "Authorization: Bearer sk_test_xxx" \
  -H "Content-Type: application/json" \
  -d '{"checkout_session": {}}'

Test Mode Behavior:

Refunds complete instantly with status: "succeeded"
No actual money movement
Reference IDs still generated for testing
Full webhook flow works

Test Credentials

For testing payments → refunds flow: Email: miguel@homefit.com Password: password Create test API keys at: http://localhost:3001/partners/dashboard/developers

Troubleshooting

Problem: “Checkout session must be complete”

Cause: Trying to refund a checkout session that hasn’t been paid or is in progress Solution:

Check session status: GET /v1/checkout/sessions/{id}
Ensure status === "complete"
Wait for payment to finish if still processing

Problem: “checkout session does not exist”

Cause: Invalid checkout session ID or doesn’t belong to your account Solution:

Verify the checkout_session_id is correct
Ensure you’re using the right API key (test vs. production)
Check that the session belongs to your partner account

Problem: Refund shows “pending” for too long

Cause: Stripe processing delay or connected account issues Solution:

Wait up to 24 hours for normal processing
Check Stripe dashboard for errors
Verify connected account has sufficient balance
Contact support if still pending after 24 hours

Problem: “Failed to create refund”

Cause: Stripe API error (usually insufficient funds in connected account) Solution:

Check connected account balance in Stripe dashboard
Ensure partner account has funds to cover refund
Review Stripe logs for specific error details
Contact Flex support with checkout_session_id

Problem: Reference ID not available

Cause: Payment network hasn’t provided ARN yet Solution:

Reference IDs typically appear within hours
Check reference_status - if pending, wait
If unavailable, payment network doesn’t provide this type
Poll /v1/refunds/{refund_id} periodically for updates

API Endpoint Summary

Endpoint	Method	Purpose
`/v1/checkout/sessions/{id}/refund`	POST	Primary - Create refund for checkout session
`/v1/refunds`	GET	List all refunds with filters
`/v1/refunds/{refund_id}`	GET	Get single refund details
`/v1/refunds/{refund_id}`	PATCH	Update refund metadata
`/v1/checkout/sessions/{id}`	GET	Get checkout session details

Common Use Cases

Use Case 1: Customer Service Full Refund

async function processFullRefund(checkoutSessionId, reason) {
  const response = await fetch(
    `https://api.withflex.com/v1/checkout/sessions/${checkoutSessionId}/refund`,
    {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${process.env.FLEX_API_KEY}`,
        'Content-Type': 'application/json'
      },
      body: JSON.stringify({
        checkout_session: {
          refund_metadata: {
            reason: reason,
            processed_by: 'customer_service',
            timestamp: new Date().toISOString()
          }
        }
      })
    }
  );

  const result = await response.json();
  const refund = result.checkout_session.refunds[0];

  console.log(`Refund created: ${refund.refund_id}`);
  return refund;
}

Use Case 2: Return Processing with Line Items

async function processReturn(checkoutSessionId, returnedItems) {
  // returnedItems = [{ productId, amount }, ...]

  const lineItems = returnedItems.map(item => ({
    product: item.productId,
    amount_to_refund: item.amount
  }));

  const response = await fetch(
    `https://api.withflex.com/v1/checkout/sessions/${checkoutSessionId}/refund`,
    {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${process.env.FLEX_API_KEY}`,
        'Content-Type': 'application/json'
      },
      body: JSON.stringify({
        checkout_session: {
          line_items: lineItems,
          amount_tax: calculateProportionalTax(returnedItems),
          refund_metadata: {
            reason: 'items_returned',
            rma_number: generateRmaNumber()
          }
        }
      })
    }
  );

  return await response.json();
}

Use Case 3: Price Adjustment

async function applyPriceAdjustment(checkoutSessionId, adjustmentAmount, reason) {
  const response = await fetch(
    `https://api.withflex.com/v1/checkout/sessions/${checkoutSessionId}/refund`,
    {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${process.env.FLEX_API_KEY}`,
        'Content-Type': 'application/json'
      },
      body: JSON.stringify({
        checkout_session: {
          amount: adjustmentAmount,
          refund_metadata: {
            reason: 'price_adjustment',
            adjustment_type: reason,
            original_ticket: 'TICKET-123'
          }
        }
      })
    }
  );

  return await response.json();
}

Additional Resources

Flex API Documentation: Contact your Flex account manager
Stripe Refund Guide: https://stripe.com/docs/refunds
Reference Numbers: https://support.stripe.com/questions/how-to-trace-a-refund-using-reference-numbers
Webhooks Setup: Contact Flex support for webhook configuration

Support

For issues or questions about refunds:

Check this guide for common solutions
Review Stripe dashboard for payment details
Contact Flex support with:
- checkout_session_id
- refund_id (if refund was created)
- Error messages
- Timestamp of the issue

​Primary Refund Endpoint

​POST /v1/checkout/sessions//refund

​Request Format

​Option 1: Line Item-Based Refund (Granular Control)

​Option 2: Simple Amount-Based Refund

​Option 3: Full Refund

​Request Parameters

​Success Response

​Error Responses

​Checkout Session Not Complete (422 Unprocessable Entity)

​Checkout Session Not Found (404 Not Found)

​Unauthorized (401 Unauthorized)

​Refund Statuses

​Reference Numbers for Tracking

​Reference Types

​Reference Status

​Complete Workflow Examples

​Example 1: Full Refund

​Example 2: Partial Refund by Line Items

​Example 3: Partial Refund by Amount

​Example 4: Multiple Partial Refunds

​Secondary Refund API

​Tracking and Listing Refunds

​GET /v1/refunds/

​GET /v1/refunds (List Refunds)

​PATCH /v1/refunds/ (Update Refund Metadata)

​Implementation Details

​Automatic Handling by Flex

​Partial Refund Behavior

​Tax, Shipping, and Discount Refunds

​Best Practices

​1. Store Checkout Session ID

​2. Verify Checkout Session Status

​3. Use Metadata for Tracking

​4. Handle Refund Webhooks

​5. Track Remaining Refundable Amount

​6. Save Reference Numbers

​7. Handle Errors Gracefully

​Testing

​Test Mode

​Test Credentials

​Troubleshooting

​Problem: “Checkout session must be complete”

​Problem: “checkout session does not exist”

​Problem: Refund shows “pending” for too long

​Problem: “Failed to create refund”

​Problem: Reference ID not available

​API Endpoint Summary

​Common Use Cases

​Use Case 1: Customer Service Full Refund

​Use Case 2: Return Processing with Line Items

​Use Case 3: Price Adjustment

​Additional Resources

​Support