Ask four vendors who sold the car and you will get four confident answers. The search agency points at the click. The retargeting vendor points at the impression. The lead reseller points at the form. The chat provider points at the transcript. Each of them is telling the truth about the part of the journey they can see, and each of them is being paid on that answer.
This is not fraud. It is a structural problem. No vendor in the chain has visibility into the other touches, so every one of them assigns full credit to itself and invoices accordingly. The dealer pays four times for one car and has no way to prove it.
What last-click actually measures
It measures which vendor was standing closest to the customer at the moment of conversion. That is a useful fact and a terrible basis for a budget. The touch that closes is rarely the touch that persuaded. A shopper who spent three weeks reading reviews, asked an assistant about hybrid running costs, and drove past your lot twice will still be credited to whichever branded search ad they clicked on the way to the finance application.
Budget follows credit. So spend migrates toward the bottom of the funnel, toward the cheapest, most attributable, least persuasive inventory you can buy. The vendors reporting the best numbers are frequently the ones doing the least work.
The thirty points nobody could see
On a rooftop running our platform, 56.9% of closed deals could be traced back to a source before we connected identity across systems. After the website, CRM, phone, chat and DMS resolved into one record per person, that figure moved to 87.4%.
The thirty points in between were not new deals. They were deals the store had already closed and already paid for, sitting in a gap between systems where every vendor could claim them and nobody could verify them. That gap is where the arguments happen, and it is roughly a third of the business.
Service revenue changes the answer
Judging a campaign on front gross alone understates a good customer badly. Attach three years of repair orders to the deal and the ranking of your sources often reverses. The channel with the higher cost per sold unit can produce customers who service with you for years, while the cheap channel produces one-time buyers who never come back.
You cannot see that difference without identity. The service lane and the sales floor have to agree on who the person is before anyone can say what the source was worth.
Four questions worth asking your vendors
- When you report a sale, are you matching against my DMS, or against your own conversion event?
- If another vendor also claims this deal, does your number go down?
- What percentage of my closed business can you account for, and what happens to the rest in your report?
- If I leave, do I keep the customer graph you built on my data?
The answers are usually more informative than the dashboard. A vendor whose reported number never moves when another vendor claims the same deal is not measuring. It is billing.
What to do instead
Stop asking vendors to grade themselves. Resolve identity first, at the dealer level, on infrastructure you control. Then reconcile spend against closed deals and the service revenue that follows, the same way you would reconcile any other account. Where the ledger cannot balance, report it as unattributed instead of spreading it across channels to make a chart look complete.
It is less flattering than a vendor dashboard. It is also the only version of the number you can act on.