Google Ads Tracking
Why Google Ads and Shopify revenue don't match
Five separate mechanics all push Google Ads' reported revenue away from Shopify's order total, usually at the same time and in different directions. Here's what's actually happening.
The five mechanics behind the gap
Google logs a conversion when the tag fires, near checkout. Shopify logs the order at the moment it's placed. A late-firing tag or a delayed webhook shifts which day's report each shows up in.
Google Ads attributes a conversion to a click within its own window, using its own model — the same structural gap covered on the Google Ads tracking page.
A Shopify app's conversion action layered on top of a manually configured Google Ads tag, both counting the same purchase.
Google Ads conversion value doesn't automatically adjust for a refund processed after the fact. Shopify's order total, meanwhile, reflects gross, net, or tax-inclusive figures depending on which report you're reading.
The same order can be credited by both Google Ads and Meta if the customer interacted with both before buying — adding the two together overstates combined attributed revenue.
Performance Max makes accurate value more important, not less
PMax's automated bidding optimizes directly against whatever conversion value it's given. It doesn't add a new source of mismatch on its own, but because it leans on conversion value more heavily than manually managed Search or Shopping campaigns, any existing tracking error — duplicate conversions, stale refund data — has a larger downstream effect on what PMax decides to spend on.
What's actually worth checking
Start with Google Ads' own conversion action settings — confirm there's exactly one primary conversion action for Purchase, not a primary and a secondary both counting. Then check whether refunds are being reported back to Google Ads at all (they usually aren't, by default). Then compare the ratio between the two systems over a stable period rather than chasing an exact daily match, which conversion-date-vs-order-date timing alone makes unlikely.
Compare your own Google Ads and Shopify numbers
Connect your store and Google Ads account to see the actual gap for your orders, not an illustrative example.