Most eCommerce setups only send purchase data to analytics platforms, leaving out one critical part of the picture: refunds and returns. Without refund tracking, your Return on Ad Spend (ROAS) is inflated and misleading, especially when using platforms like Google Ads, Meta, and GA4.

By using Server-Side Tagging with OpenCart, we can accurately track refunded transactions and send them back to your analytics tools—ensuring true revenue-based attribution.

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✅ Why Track Refunds?

Reason	Impact
Clean ROAS	Exclude refunded revenue from conversions
GA4 Attribution Accuracy	Maintain realistic funnel reporting
Google Ads Optimization	Avoid over-optimized bids for refunded conversions
Meta Ads CAPI	Refund signals improve campaign quality

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🧰 Requirements

Item	Description
OpenCart	Version 3.x or 4.x
Server-Side GTM	Configured on a first-party domain
Google Ads, Meta CAPI, GA4	Platforms integrated
Order Status Logic	To determine when an order is refunded
Consent Layer (Optional)	To handle GDPR/CCPA compliance

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🧱 Step 1: Detect Refunded Orders in OpenCart Admin

Modify the refund trigger. In OpenCart, you can hook into order status updates.

In admin/controller/sale/order.php, locate or add code where order status is updated to “Refunded” (you may need to define a custom status ID, e.g., 11):

if ($order_status_id == 11) { // 11 = Refunded
    $order_info = $this->model_sale_order->getOrder($order_id);
    $products = $this->model_sale_order->getOrderProducts($order_id);

    $items = [];
    foreach ($products as $product) {
        $items[] = [
            'item_id' => $product['model'],
            'item_name' => $product['name'],
            'quantity' => $product['quantity'],
            'price' => $product['price']
        ];
    }

    $refund_payload = [
        'event_name' => 'refund',
        'event_id' => uniqid('refund_', true),
        'transaction_id' => $order_info['order_id'],
        'currency' => $order_info['currency_code'],
        'value' => -1 * $order_info['total'],
        'items' => $items
    ];

    $this->sendRefundToServer($refund_payload);
}

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🔌 Step 2: Send Refund Event to Server-Side GTM

Add this custom helper function in the same file or a reusable module:

private function sendRefundToServer($payload) {
    $ch = curl_init('https://gtm.yourdomain.com/event');
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($payload));
    curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type:application/json']);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_exec($ch);
    curl_close($ch);
}

✅ This will trigger every time an order is marked as refunded.

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🧠 Step 3: Parse Refunds in Server GTM

In your Server Container:

1. Use the HTTP Request Client
2. Match incoming event where event_name = refund
3. Extract transaction_id, items, value, currency, and event_id

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📤 Step 4: Send Refund Event to GA4 via Server GTM

Create a GA4 Event Tag in ssGTM:

Parameter	Value
Event Name	refund
Transaction ID	{{transaction_id}}
Value	{{value}}
Currency	{{currency}}
Items	{{items}}
Event ID	{{event_id}}

✅ This removes refunded purchase value from revenue reports in GA4.

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🎯 Step 5: Send Refund to Google Ads

In ssGTM:

1. Create a Google Ads Conversion Tag
2. Configure:
   • Conversion ID / Label
   • transaction_id: {{transaction_id}}
   • value: {{value}} (should be negative)
   • currency: {{currency}}
   • event_id: {{event_id}} (deduplication)

✅ This tells Google Ads the conversion has been reversed.

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📘 Step 6: Send Refund Event to Meta Conversions API

Use the Meta HTTP tag or a Custom Request:

POST https://graph.facebook.com/v18.0/<PIXEL_ID>/events?access_token=<TOKEN>

{
  "data": [{
    "event_name": "Refund",
    "event_time": {{ timestamp }},
    "event_id": "{{event_id}}",
    "action_source": "website",
    "custom_data": {
      "transaction_id": "{{transaction_id}}",
      "currency": "{{currency}}",
      "value": -99.00
    }
  }]
}

✅ Meta will treat it as a revenue correction.

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🛡️ Step 7: Consent-Safe Processing

If you’re passing PII (e.g., email for Enhanced Conversions), add this logic:

if ($user_consent_given) {
    $payload['email'] = hash('sha256', strtolower($order_info['email']));
}

Or handle consent_granted logic in ssGTM to block tags if needed.

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🧪 Step 8: QA Your Refund Events

Tool	What to Check
ssGTM Preview	Inspect payload structure
GA4 DebugView	Look for real-time refund event
Google Ads Conversion Tag Diagnostics	Check negative conversion
Meta Events Manager → Test Events	View refund test data

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📊 Sample Refund Data Sent

{
  "event_name": "refund",
  "event_id": "refund_664c49d1a3bc9",
  "transaction_id": "ORD12842",
  "value": -99.99,
  "currency": "USD",
  "items": [{
    "item_id": "PROD001",
    "item_name": "Winter Jacket",
    "price": 99.99,
    "quantity": 1
  }]
}

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✅ Benefits Summary

Feature	Benefit
True ROAS Calculation	Filter out refunded revenue
Attribution Accuracy	GA4 funnel metrics adjusted
Ads Optimization	Less bias in Smart Bidding or CAPI
First-Party Secure	No exposure of refund logic in frontend
Works with All Platforms	Google Ads, Meta, GA4, and others

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