Agreeing the number

This guide is for the person who will be asked to approve the spend and then, eighteen months later, to say whether it worked. Almost all of the difficulty in that second conversation is created by decisions taken in the first one.

A definition has four parts

• The computation. Precise enough that two analysts working separately produce the same figure.
• The exclusions. What is deliberately left out, and why. This is where every later dispute originates.
• The owner. A named person whose figure this is, not a department.
• The version. Because it will change, and when it does the change should be a release with a date, not a quiet edit.

The exclusions people forget

• Tender or contract business, which follows different mechanics and swamps a median if left in.
• Revisions of the same requirement, which inflate volume if counted separately.
• Items past a staleness threshold, which should be marked dead rather than left open.
• Volume won centrally and merely billed through a channel, which distorts every channel metric.
• Intercompany and warranty transactions, which are not commercial events.

Four questions for the vendor

One. Which single number moves, and who owns it? Two. Is it computable from data we already keep, with no new collection process? Three. What does the contract say happens if the pilot does not clear it? Four. Who reports the result, us or you?

On that last one, insist on your own team. A benefit computed by the vendor is a marketing claim wearing a spreadsheet.