Why do refund windows get missed?

Drift rather than decision: waiting for month-end data, waiting for the person who can judge it, or building an integration first. Each is a failure to have a date in the calendar rather than a failure of judgement.

What actually expires during an evaluation?

Your analytics retention setting, not usually the refund window. If retention is short, the historical period you wanted to evaluate against can disappear mid-evaluation. Check it on day one; it is the only real deadline in the process.

Attribution refund windows expire quietly

Refund windows are missed by drift rather than decision. Three ways evaluations quietly overrun, and the two-line calendar habit that prevents each of them.

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By Joris van Huët, Founder & CEOUpdated 2026-10-063 min read

Refund windows lapse through drift, not decision, and the vendor has no reason to remind you. Three patterns account for almost all of it.

The three drifts

Drift	How it happens	Cost
Waiting for the right data	"We will evaluate properly after month end"	The window closes before month end does
Waiting for the right person	The one who can judge it is on holiday	Two weeks of a four-week window
Waiting for the integration	Somebody decides to build the pipe first	The whole window

The third is the most expensive and the most common. Building an integration before deciding whether the tool is any good consumes the evaluation period and creates a sunk cost that biases the eventual decision.

The calendar habit

Two lines, entered on day one. The last day of the window, and a reminder three days before with the words "decide or request". That is it. It sounds trivial and it prevents all three drifts, because each of them is a failure to have a date rather than a failure of judgement.

What to evaluate if time is already short

If half the window is gone, run the two checks that need the least setup. Point the tool at a past period where you already know what happened, and point it at a channel too small to measure. The first tests whether the method reproduces something true; the second tests whether it admits its limits.

Both fit in an afternoon and together they are a defensible verdict. The full sequence is in testing an attribution tool inside its refund window.

The structural way to avoid the problem

Prefer a commitment with no window at all. A one-time purchase has no clock running underneath it, so an evaluation that takes six weeks costs the same as one that takes six days.

That is the shape of the €99 read: once, no subscription, full refund within 30 days, no questions asked, and nothing installed because the input is a Google Analytics export you already hold. Pro at €299 a month is cancellable at any time and is a separate decision, taken after the first read rather than before it.

What genuinely does expire

One thing, and it is not the refund window: your analytics retention setting. If it is short, the historical window you wanted to evaluate against can disappear while the evaluation is still going, which is covered in the two-month retention trap.

Check that setting on day one of any evaluation. It is the only real deadline in the process and nobody mentions it.

The honest note on urgency

Nothing here is urgent because a vendor says so. It is urgent because calendars drift and retention settings expire, and both are your responsibility rather than the vendor's.

Frequently asked questions

Why do refund windows get missed?
Drift rather than decision: waiting for month-end data, waiting for the person who can judge it, or building an integration first. Each is a failure to have a date in the calendar rather than a failure of judgement.
What can I evaluate if half the refund window is gone?
Two checks that need almost no setup. Run the tool on a past period where you already know what happened, and point it at a channel too small to measure. Together those are a defensible verdict in one afternoon.
What actually expires during an evaluation?
Your analytics retention setting, not usually the refund window. If retention is short, the historical period you wanted to evaluate against can disappear mid-evaluation. Check it on day one; it is the only real deadline in the process.

Go deeper: Incrementality testing, explained.

Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.

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