Several channels can claim the same purchase.
All 100 purchases in this example are claimed by at least one channel. Adding channel reports counts shared purchases twice. MER uses store revenue and total marketing spend; it does not determine causal lift.
Why the numbers can't add up
Have you ever added up Meta's, Google's and TikTok's reported revenue and found a number bigger than your actual revenue? You're not alone — and it isn't a spreadsheet error. It's how attribution works: each platform credits itself for the same sales with its own generous windows.
Combined with Meta's default window of 7-day click and 1-day view — where even a view without a click can trigger credit — the attributed ROAS gets systematically inflated. The dashboard isn't lying on purpose; it's just showing each channel's own, inflated version of reality.
What to trust instead
The solution isn't to find the "right" attribution model — they all have a built-in bias. The solution is to supplement with metrics that can't be inflated: MER (total revenue against total spend) tells you whether the whole machine makes money, and incrementality tests tell you what a channel actually created.
Use attribution for direction, not for a verdict. Read the individual channels' ROAS as indicators, but make budget decisions on the total. That's the difference between optimizing a dashboard and optimizing your bank account.
Frequently asked questions
Why does the sum of my channels' ROAS exceed my actual revenue?
Because each platform credits itself for the same sales with its own generous conversion windows — they double-count. Add up their reported revenue and you're counting the same orders several times.
What should I trust instead of platform ROAS?
MER (total revenue against total spend), which can't be inflated by attribution, supplemented with incrementality tests for the big decisions. Use attribution for direction, not for the final verdict.
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About the author
Nicklas Segatz Mortensen
Growth hacker and fractional CMO with 10+ years' experience and hundreds of millions in managed ad spend behind him. Background from larger Danish and international scale-ups, and from the agency world.
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