Why GA4 revenue and Meta or Google revenue never match

The revenue the ad platform reports is almost always higher than GA4's for two reasons: each platform uses a different attribution window and credits itself for sales that happened days after the click, and several platforms credit themselves for the same sale, so adding up what each one reports reaches a total higher than you actually sold.

If you've ever compared what the ad manager says you sold with what Google Analytics recorded, you know the numbers rarely match. This isn't a bug or a configuration error. It's how each system was built to count. Understanding why changes the way you decide where to invest.

Reason 1: different attribution windows

Each platform decides on its own how long after a click it still considers the sale its own merit. One might count a purchase that happened seven days after the ad. Another, one day. Since the windows differ, the same sale enters one's count and not the other's, or enters both. There is no agreement between them about who got the credit, because each was built to show its own work in the best possible light.

Reason 2: the same sale counted several times

This is the most important and the least noticed. A customer often sees an ad on Meta, then searches on Google, then enters through the site. When the purchase happens, each of these platforms credits itself for the whole sale. If you open all three dashboards, they all show the sale as theirs. Adding up what each one reports is counting the same sale three times.

That's why the sum of the revenue reported by the platforms almost always exceeds real revenue. It's not that each one is lying. It's that none of them knows what the others are counting, and none has an incentive to discount the others' share.

Which one to use as the truth

The most reliable yardstick tends to be a source that has no interest in crediting itself for the sale. GA4, being independent of the ad platforms, plays that role well in most cases: it records the sale once and attributes it to one origin, without inflating. It's not perfect, no measurement is, but it errs less and without bias in anyone's favor.

There are exceptions, and recognizing them is part of doing this well. When the business has its own sales system that's more reliable than GA4 for that flow, it's that system that becomes the revenue truth. The principle isn't "always use GA4," it's "use the most reliable independent source for that business."

What's at stake

Trusting platform revenue as if it were real has concrete consequences. You believe you sold more than you did. You calculate a return on investment that doesn't exist. And, most costly, you allocate budget based on that inflated return, putting more money where the number looked good but was only overlapping credit. It's like measuring with a ruler that always pulls in your favor: the reading is good, reality doesn't follow.

Frequently asked questions

Why does the ad platform show more sales than GA4?
Each platform uses a different attribution window and several credit themselves for the same sale. Adding up what each one reports reaches a total higher than what you actually sold.

Which revenue should I use as the truth?
In most cases, an independent source like GA4, because it has no interest in crediting itself for the sale. When the business has its own more reliable sales system, that system becomes the truth.

So is Meta's or Google's attribution useless?
It works as a compass, not as a ruler. To compare ad sets within the same platform and decide quickly, it works. What it shouldn't do is define how much you actually sold.

What happens if I trust platform revenue?
You tend to think you sold more than you did, calculate a ROAS that doesn't exist and make budget decisions based on an inflated return.