Funnels look simple on a slide and almost never are in the database. The shape that matters is the one your analyst can reproduce.

The short version: a funnel chart you would put your name to is mostly a matter of doing the obvious thing carefully. Define each step as a named event, capture it in one canonical place, and reconcile the totals against your billing system at least monthly.

You are choosing rigour over speed of reporting. That is the right trade for anything you base spending decisions on. That trade-off is the one most teams underweight when they plan the work, and it is the one that quietly determines whether the project ships on time.

If you want a longer treatment, we have a deeper post in the series. For now, the takeaway is small enough to fit on a sticky note: A funnel that has been reconciled against revenue once is worth ten funnels that have not.