GA4 Purchase Event Parameters: What's Required, What's Recommended

The truly required parameters

GA4 will record a purchase event without any parameters. But for revenue to appear in monetisation reports and be attributed to the purchase, two parameters are mandatory:

• currency: A valid ISO 4217 three-letter currency code (GBP, USD, EUR, etc.). Not the currency symbol. Not a number. Exactly three uppercase letters matching the code list. If this is absent or invalid, GA4 records the event but shows zero revenue. See our piece onresolving GA4 currency mismatchesfor the most common formatting mistakes.
• value: The monetary value of the transaction as a number. Not a string. Not a formatted string with a comma separator. The number 49.99, not the string '49.99' or '$49.99'. If value is missing or is zero, revenue is reported as zero.

These two parameters are the most frequently broken. Use DebugView with a test purchase to confirm both are present with correct formats. If you have already confirmed the event fires but revenue is still zero, our diagnostic onfixing missing revenue in GA4 purchase eventswalks through every other root cause.

The strongly recommended parameters

• transaction_id: A unique string identifying this transaction, typically your order ID or order number. This is required for GA4's deduplication mechanism to work correctly. If you combine client-side and server-side purchase tracking via the Measurement Protocol, a matching transaction_id in both events allows deduplication. Our breakdown ofduplicate transactions in GA4covers the dedup edge cases when IDs go missing or differ in format.
• items: An array of product objects representing what was purchased. Without this array, your Ecommerce Purchases report shows transaction-level data but no product-level data. You cannot see which products were purchased, their revenue contribution, or performance by product category.

Each object in the items array should include at minimum:

• item_id: a unique product identifier, typically the SKU or product ID
• item_name: the product name as it should appear in reports
• price: the unit price of the product (not total line price)
• quantity: the number of units purchased

Item-level parameters worth including

Within each item object, additional parameters provide richer product analysis:

• item_brand: the brand of the product
• item_category through item_category5: product category hierarchy, allowing analysis by category tree
• item_variant: the specific variant purchased (size, colour)
• discount: the discount amount applied to this specific item
• item_list_name: the list from which the product was added to cart (e.g., search results, homepage recommendations, category page)

The item_list_name and item_list_id parameters link view_item_list events to the eventual purchase, enabling add-to-cart rate and purchase rate calculations at the product list level. These require consistent population across all ecommerce events in the funnel, not just the purchase event. Our wider walkthrough ofGA4 ecommerce tracking checksshows how each event in that chain should be validated.

Common implementation errors

• value includes tax and shipping: Compare your GA4 total revenue to your net revenue excluding tax and shipping in your store backend. If GA4 revenue is consistently higher by a percentage matching your average tax rate, value is being sent with tax included.
• Empty items array: An items array that is present but contains no objects (items: []) causes all product-level reports to show zero items. The array must contain at least one product object per purchase.
• price as total line price instead of unit price: If a customer buys 3 units at £10 each, price should be 10 and quantity should be 3. If price is sent as 30 (the total), GA4 will show inflated per-unit prices and incorrect revenue when quantity is taken into account.