Sales attribution: the only two paths that exist

Every sale attribution falls into one of two mechanisms. Understanding both — and where each one breaks — explains most of the sales that show up as "unknown source".

Whatever the tool, tying a sale to a source uses one of two mechanisms. Everything else is an implementation variation.

Path 1: the parameter that travels

You stamp a session identifier onto the checkout link — usually in a tracking field the payment platform returns in its webhook. When the sale happens the identifier comes back, and you know exactly which session bought.

It is the precise path. It is also the one that breaks most:

• The payment platform truncates the tracking field at a character limit — and whatever sits at the end disappears.
• The person copies the link and sends it to someone else, or opens it in another browser.
• A redirect along the way drops the query string.
• The checkout is opened through a direct link, never touching the page.

Truncation is the most treacherous one: it raises no error, appears in no report, and the identifier arrives half-formed — unreadable and indistinguishable from "never sent".

Path 2: identity

When the parameter does not arrive, the buyer’s email remains. If that email already exists in your base tied to a lead, and that lead has browsing history, you know where they came from — with no parameter on the sale at all.

This path is more forgiving and less precise: it recovers the sale but attributes it to the person’s known source, which may be weeks old. For media decisions that is usually enough; for fine-grained reporting it needs to be labeled as such.

The rule that prevents double counting

The two paths must coexist under a clear hierarchy: a sale explained by the parameter is never re-counted by identity. Without that rule the same sale enters the report twice and your return doubles on its own.

1. 01Try the tracking parameter. If it arrived complete and readable, the sale belongs to that session.
2. 02If it did not, try identity through the buyer’s email and phone.
3. 03If neither resolves, mark it unattributed — and keep that visible.

What to do with the unattributed share

The temptation is to distribute it proportionally across campaigns to "close the books". That turns an honest number into an invented one wearing the costume of rigor. The unattributed share is information: if it grows, something broke in collection — and it is much better to find that out by watching the metric than six months later, when the entire history is already contaminated.

A good first step if your unattributed percentage is high: check whether the session identifier sits at the beginning of the checkout link’s tracking field rather than the end. When truncation happens, whatever is at the end is always the casualty.