GA4 E-commerce Tracking: The 12 Checks That Matter Most

Purchase Event Integrity Checks

The foundation of e commerce tracking is the purchase event, and it breaks in more ways than most teams realise.

Check 1: verify that transaction_id is present on every purchase event, missing transaction IDs make deduplication impossible.

Check 2: confirm transaction_id values are unique per order rather than recycled session identifiers.

Check 3: validate that the value parameter matches the actual order total, including tax and shipping if that is your convention, inconsistent value definitions cause revenue to diverge from your backend records.

Check 4: ensure the currency parameter is populated and consistent across all events. Check 5: confirm that items array is present and contains at least one item with item_id, item_name, price, and quantity.

Check 6: compare GA4 purchase event counts against your order management system for the same date range, a variance above 2 to 3% warrants investigation.

These six checks alone will surface the majority of purchase tracking failures before they compound into weeks of bad data.

Funnel Event Coverage and Parameter Quality

Beyond the purchase event, GA4 e commerce relies on a sequence of funnel events: view_item_list, view_item, add_to_cart, begin_checkout, add_payment_info, and purchase.

Check 7: confirm all funnel events are firing and that the items parameter is consistently populated throughout, not just on the purchase event.

Check 8: validate that item_list_id and item_list_name are populated on view_item_list and select_item events so product list performance reports are usable.

Check 9: check that add_to_cart events fire reliably for both standard add to cart actions and quantity changes.

Check 10: verify begin_checkout fires once per checkout initiation, not on every page load during the checkout flow, duplicating this event inflates funnel metrics and makes conversion rate calculations misleading.

Refunds, Currency, and Duplicate Transactions

The last two checks address recurring revenue accuracy problems.

Check 11: verify that your refund implementation is sending the refund event with the correct transaction_id, if refunds are being tracked without matching transaction IDs, GA4 cannot reconcile them and your net revenue figures will be inflated.

Check 12: audit for duplicate purchase events on order confirmation pages. This is the most common e commerce tracking bug.

It happens when the confirmation page can be reloaded, or when both a GTM trigger and a hard coded tag fire simultaneously.

Duplicate transactions inflate revenue, throw off ROAS calculations in Google Ads, and corrupt BigQuery exports.

A transaction_id deduplication check over a rolling 30-day window will quantify the scale of the problem and help you prioritise the fix.