Scope creep is usually described as a discipline problem. More often it is a documentation problem. Most project documents describe what will be built and say nothing about what will not be, which means every request that arrives later is arguably inside the agreement. Nobody ever agreed it was outside.
Write the exclusions first
Before phase one begins we write two lists. The first is what phase one delivers. The second is what phase one does not deliver, and it is usually the longer of the two.
The second list is not a refusal. It is a schedule. The items on it are real, they are wanted, and they are not now. Writing them down does two things: it stops them arriving as surprises, and it lets the price of phase one hold, because that price was quoted against a boundary rather than against a hope.
What tends to go on it
- The reports nobody has specified yet.
- The second language.
- Connections to systems that are themselves being replaced this year.
- The permissions model for a team that does not exist yet.
- The mobile version.
- The parts of the old system still in daily use that nobody can currently explain.
Every one of those is legitimate work. Every one of them also ends projects when it arrives unannounced in week six.
Why the timing is the whole point
An exclusion written after the work starts is a negotiation. Written before it starts, it is a decision.
The same sentence does different work depending on when it was written, and only one of those two moments is calm. Afterwards there is a budget under pressure, a date already promised to someone, and two parties who each believe they remember the conversation correctly.
This is also why phase one carries a fixed price. A fixed price is only honest when both sides know precisely what sits outside it.