How Google Was Counting Every Sale 3 Times — And Destroying Smart Bidding

The situation

An Australian home furniture store was running $30K/month on Google Ads. Their Google Ads dashboard showed a CPA of $22 — well within their target of $35. But when the owner compared Google's claimed revenue against actual Shopify orders, the numbers didn't come close to matching. Google was significantly overclaiming.

The problem

Three separate conversion actions were all counting the same purchase simultaneously: a GA4 goal imported into Google Ads, a conversion tag fired directly from GTM, and a manually created conversion action set up by a previous agency. Every single Shopify purchase was being recorded up to 3 times in Google Ads. Smart Bidding — which uses conversion data to decide how much to bid on each keyword — believed the account was performing 3× better than reality. The true CPA was $89, not $22. The algorithm was underbidding on high-value keywords and overspending on low-intent ones.

What we did

1. Audited all active conversion actions in Google Ads — found 3 all tagged as primary conversions counting the same purchase
2. Removed the 2 redundant conversion actions, leaving a single purchase conversion action as the sole primary signal
3. Set up Enhanced Conversions with SHA-256 hashed customer email — gives Google better identity matching for iOS users and logged-out browsers
4. Restructured the conversion action hierarchy: one primary purchase action, with add-to-cart and initiate-checkout as secondary (used for observation, not bidding)
5. Allowed Smart Bidding 3 weeks to recalibrate with clean data before evaluating performance

Why it worked

Smart Bidding is only as good as the data it learns from. When the same conversion is counted multiple times, the algorithm builds its entire model on inflated signals — it will always underbid because it thinks it's already hitting target. The fix here wasn't just technical; it required patience to let Smart Bidding rebuild its model with honest data before judging performance.