Why Ads and Analytics will never agree
Google Ads reports 47 conversions. GA4 reports 31 from paid search. Somebody asks which is right.
Neither. They are answering different questions, by design, and a large part of PPC reporting time is wasted trying to make them agree.
The four reasons they differ
Attribution timing. Google Ads credits a conversion to the date of the click, not the date of the conversion. GA4 credits it to the date of the session in which it happened. A click on the 28th converting on the 3rd appears in different months in the two systems. This alone accounts for most month-boundary discrepancies.
Attribution model. Ads reports conversions attributed to ad interactions, including view-throughs and engaged views for some campaign types. GA4 uses its own model across all channels, and paid search must share credit with everything else in the path.
Conversion definition. The conversion actions in Ads and the key events in GA4 are configured separately, by different people, at different times. They frequently are not the same set.
Identity and consent. The two systems resolve users differently and are affected differently by consent state, ad blockers and cross-device behaviour.
Which to use for what
Use Google Ads for bidding decisions. It is the number the bidding algorithm is optimising against. Arguing with it is arguing with the mechanism.
Use GA4 for cross-channel comparison. It is the only place where paid search sits next to organic, direct and referral on comparable terms.
Use your own back-end for revenue. Neither platform knows about refunds, cancellations, or the deal that closed six weeks later at a different value.
The reconciliation worth doing
Not exact matching — trend matching. If both systems show paid conversions rising 20% month on month, the account improved. If Ads shows a rise and GA4 shows a fall, something changed in measurement, and that is the finding worth chasing.
A stable ratio between the two numbers is a healthy sign. A ratio that suddenly moves is a tag problem, a consent change, or a conversion action edit — and it is far more diagnostic than either number alone.
What to tell a client
"These two numbers count differently on purpose. Here is the one we make decisions with, here is the one we compare channels with, and here is the one finance uses." Said once, clearly, it prevents the same meeting recurring monthly.