Attribution
Platform Overclaim
The gap between what an ad platform reports as conversions and the true incremental conversions the ads actually caused. It arises because platforms use broad attribution windows, count view-through conversions generously, and take credit for conversions that were already going to happen, which is why the effect concentrates on retargeting and branded search where intent already existed. The direction is not universal, and treating it as universal is the common error: measured against 640 Meta incrementality experiments, Haus found Meta under-reporting incrementality on 7-day click for direct-to-consumer advertisers, while Advantage+ campaigns over-reported relative to Manual ones. Because direction and size depend on campaign type and attribution setting, overclaim has to be measured per account through controlled incrementality testing rather than corrected with a fixed per-platform coefficient.
Why it matters
It is the reason channel ROAS figures sum to more revenue than the business earned. Every platform claims the conversions it touched, and the same purchase is claimed several times. What it is not is a fixed haircut you can apply per platform, because the same study that shows one campaign type over-reporting shows another under-reporting on the same platform.
In practice
Add up platform-reported revenue across channels and compare it to actual revenue. The ratio is your overclaim factor and it is usually the fastest way to make the problem legible to a finance team.
Related terms