GA4 - Purchase Event

<head>
    <!-- Google tag (gtag.js) -->
    <script async src="https://www.googletagmanager.com/gtag/js?id=TAG_ID"></script>
    <script>
        window.dataLayer = window.dataLayer || [];
        function gtag(){dataLayer.push(arguments);}
        gtag('js', new Date());

        gtag('config', 'TAG_ID');
    </script>
</head>

<body>
    <div>This is where the purchase form would go</div>
<script>
    gtag("event", "purchase", {
        transaction_id: "T_12345_1",
        affiliation: "Google Merchandise Store",
        value: 25.42,
        tax: 4.90,
        shipping: 5.99,
        currency: "USD",
        coupon: "SUMMER_SALE",
        items: [
        // If someone purchases more than one item,
        // you can add those items to the items array
         {
          item_id: "SKU_12345",
          item_name: "Stan and Friends Tee",
          affiliation: "Google Merchandise Store",
          coupon: "SUMMER_FUN",
          discount: 2.22,
          index: 0,
          item_brand: "Google",
          item_category: "Apparel",
          item_category2: "Adult",
          item_category3: "Shirts",
          item_category4: "Crew",
          item_category5: "Short sleeve",
          item_list_id: "related_products",
          item_list_name: "Related Products",
          item_variant: "green",
          location_id: "ChIJIQBpAG2ahYAR_6128GcTUEo",
          price: 9.99,
          quantity: 1
        }]
    });
    </script>
</body>