Never pay for an order you already own. Settle attribution in January, in writing.
Your replenishment flow and your retargeting ads chase the same customers every week. The jar runs low and the reminder lands. On the way to your site, the customer clicks a dynamic product ad for the item they were already rebuying. The ad platform books the order on its click window. Your flow report shows revenue softening. Together the two reports claim more than the store sold.
Next quarter, budget follows the numbers. Money moves from the program that made the demand to the channel that intercepted it. The orders keep arriving on momentum for a while, then fall off. The blame lands on the flow, because its report is the one that looked weak.
The retargeting ad did not create that order. It stood in the doorway and took credit for it, and your reporting stack agreed.
A showroom has the same problem with more doors. In my years at Gallery Furniture, one sofa could be touched by a showroom associate, an outbound salesperson and a digital ad. At month end, all three could claim it. Each claim would be defensible in its own tool, and none of the tools could see the other two.
The Doorway Rule removes the conflict at the source. No paid retargeting to a customer inside an active post-purchase or replenishment window. A good share of retargeting ROAS on existing customers can be replenishment you already had. Suppressing it saves some spend, and it makes both channels readable, because paid stops booking orders it didn't cause and the flow's number means something again.
Set the window from your own repeat timing, not a platform default. Find the day your second orders cluster. Run the window from a few days after purchase to two or three weeks past that cluster. The audience is every customer with a purchase inside that window and an owned sequence still running. Update the exclusion every day, because the window moves in days and a weekly update leaks.
Exclude dynamic product ads for items the customer already owns. Those ads pay to show someone what they're already rebuying. When the owned sequence ends without an order, lift the exclusion and let paid have them. Permanent suppression is its own mistake; it costs you the paid team's agreement. Only upload customers your privacy policy lets you share with ad platforms, and leave out anyone who opted out.
Check that it bites. Match rates on customer lists run well below 100%, and Advantage+ and Performance Max campaigns can limit or override exclusions. Confirm in each platform that the audience is being excluded, not just uploaded. Where the campaign type won't honor it, use the platform's existing-customer controls, or accept a partial fix and say so.
Agree the rules on one page before the numbers exist and anyone's bonus rides on them. The January page names the click window, whether view-through counts, the attribution model, the one tool that is the source of truth for revenue, and the tie-break rule for when two reports disagree. The paid lead signs it before the quarter opens, because an unsigned page gets reopened the first time a number disappoints.
It is a five-minute conversation in January and an unwinnable one in April, when each party is defending a number already reported upward. In a seasonal business, sign it before the season opens.
Once a quarter, add up the revenue every channel claims and subtract what the store recorded. The excess is the double count. Report it as one line, without commentary, and watch it shrink. When two claims collide on one order, a one-question post-purchase survey asking where the customer first heard of you is the cheap tie-breaker.
A holdout settles what the argument can't. The control group's revenue already includes every paid conversion those customers made, so no window setting changes the gap between the groups. Attribution Isn't Proof sets one up. Bring its read when the budget conversation turns adversarial.
The paid team is not your opponent here. They read their dashboard correctly, the same as you read yours, and the conflict lives in the measurement system. You can be right about attribution and still lose, because becoming the person who raises it in every meeting is a reputation that outlasts any argument you win.
So hold the fight to two dates a year. Sign the page in January and report the measured read on the agreed date. In between, report owned revenue as a share of store revenue, keep the suppression audience current, and talk about the work.
Match last quarter's retargeting conversions to customers inside an active replenishment window. If few of them were, your paid team already suppresses; go straight to the January page.
This is one chapter of The Second Order, which is free and readable in full on a single page with no form in front of it.