MoSCoW Prioritisation

MoSCoW prioritisation is a method for agreeing what matters most before work begins, by sorting requirements into four categories. The capital letters spell the name; the lowercase o's are just filler:

• Must have — non-negotiable. Without it, the delivery has failed. If a single Must is not met by the deadline, the release is not viable.
• Should have — important but not vital; painful to leave out, but the result still works without it.
• Could have — desirable; included if time and budget allow, dropped first when they do not.
• Won't have (this time) — explicitly out of scope for now. Naming these prevents them quietly creeping back in.

The technique was devised by Dai Clegg and is most associated with the DSDM / Agile Business Consortium approach to agile delivery.

Why it matters

MoSCoW's power is in its two least glamorous categories. The Won't have list is an explicit defence against scope creep: when something is named as out of scope, adding it back becomes a visible decision rather than a quiet favour. And a disciplined Must have set — kept deliberately small, ideally well under two-thirds of the effort — is what protects the deadline. When time runs short, you sacrifice Coulds and Shoulds, not the date, because the Musts were agreed to be the only truly essential work.

Using it well

MoSCoW decides what matters; it does not decide sequence. Pair it with the critical path to know which Must-haves also gate the finish date, and with a clear definition of done so "Must have" means the same finished standard to everyone. The common failure is inflation — when every requirement becomes a Must, the method has told you nothing, because a list where everything is essential cannot protect anything.