How to track coupon and discount-code usage in GA4

If you run discount codes, you want to know which ones drive sales and which just hand away margin on orders you would have won anyway. GA4's ecommerce events can capture the coupon on every order, if you send it.

Where coupon data lives in GA4

GA4's ecommerce spec has a coupon field, available at both order level and item level on the purchase event. If your data layer includes the code the customer used, GA4 will store it against the order and the products.

How to send it

• Add the coupon value to your purchase event in the data layer when an order with a code completes.
• Pass it through your GA4 purchase event in Google Tag Manager.
• Register coupon as a custom dimension if you want to slice standard reports by it.

What to do with it

Compare revenue, order count and average order value by coupon to see which codes bring genuinely new business versus which get stacked onto orders that would have converted anyway. Watch for a single code quietly attached to most orders, that is margin leaking. Clean ecommerce tracking is the prerequisite here: if your item data is missing, the coupon data usually is too.

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