A founder told me last month he was proud of his CAC.
£41, holding steady, while everyone around him watched theirs climb.
He could not work out why the bank balance kept disagreeing with the ad account.
The answer was a number he had never put next to his CAC: his return rate. It was 35%.
So his real cost to acquire a customer he actually kept was not £41. It was £63. He had paid full price for a third of his orders, then refunded them.
True CAC = headline CAC divided by one minus your return rate.
Run it once and your whole P&L starts telling the truth.
Most founders respond to a CAC problem by attacking the CAC. New creative, new agency, another round of audience tests. The leverage is in the denominator: the return rate, the retention rate, the mix.
Paid did not stop working. It just stopped subsidising a business that was leaking at the back.
Bookmark this before your next planning call. Send it to the operator who is about to switch agencies again.