The following code is to be inserted in checkout.liquid immediately before {{ checkout_scripts }}
<!-- Google Tag Manager App Start --> <script> if (window.location.href.includes('thank_you') !== true) { var Shopify = []; Shopify["shop"] = "{{ shop.permanent_domain }}"; function loadjQuery(url, success){ var script = document.createElement('script'); script.src = url; var head = document.getElementsByTagName('head')[0], done = false; head.appendChild(script); script.onload = script.onreadystatechange = function() { if (!done && (!this.readyState || this.readyState == 'loaded' || this.readyState == 'complete')) { done = true; success(); script.onload = script.onreadystatechange = null; head.removeChild(script); } }; } if (typeof jQuery == 'undefined'){ loadjQuery('https://code.jquery.com/jquery-3.6.1.min.js', function() { jQuery('head').append('<script src="https:\/\/gtmfsstatic.getgoogletagmanager.com\/js\/gtmfsv2.js?shop={{ shop.permanent_domain }}"><\/script>'); }); } else { jQuery('head').append('<script src="https:\/\/gtmfsstatic.getgoogletagmanager.com\/js\/gtmfsv2.js?shop={{ shop.permanent_domain }}"><\/script>'); } } </script> <!-- Google Tag Manager App End -->