Ad platforms bid using the conversion data you send them. When that data is incomplete, the algorithm does not stop, it just optimises toward whatever it can still see. That is how accounts end up spending confidently in the wrong places.
What actually broke
- Intelligent Tracking Prevention caps script-set cookie lifetimes, so returning-visitor conversions get attributed to the wrong source or to nothing.
- Ad blockers and consent tools stop the client-side tag firing at all for a meaningful share of traffic.
- Long consideration windows mean the conversion happens after the attribution window has already expired.
- Form fills get counted as conversions when the thing you actually care about is a closed sale weeks later.
The rebuild, in order
- Audit what is firing today, including duplicates. Double-counted conversions are more common than missing ones and they skew bidding harder.
- Move to server-side tagging so conversions are sent from your server rather than from a browser that may block them.
- Wire the Conversions API on Meta and enhanced conversions on Google, with hashed identifiers so matching survives cookie loss.
- Import offline conversions. Send closed revenue back to the platforms so bidding targets money rather than form submissions.
- Verify end to end with test conversions before trusting a single reported number.
What the fix is worth
On one home services account, tracking had been double-counting for months. Reported cost per lead looked healthy while cost per booked job climbed. After the rebuild and offline import, cost per booked job fell from 412 to 168 dollars, and 31 percent of spend that had been going to campaigns with no real revenue attached was reallocated.
Nothing about the creative or the budget changed in that first month. The account simply started optimising against the truth.
Do this before you scale spend
Increasing budget on an account with broken measurement scales the error, not the result. Fix measurement first. It is usually two to three weeks of work and it changes every decision that follows.