Principle
Keep mitigation work out of the hidden buffer
Planned risk reduction is still planned work.
When it fits
- A known prevention task is buried inside contingency because it may not feel like 'real work.'
When to avoid it
- Organizations use different accounting conventions; preserve the conceptual distinction even if financial labels differ.
Why it matters
Put deliberate prevention and mitigation activities—tests, rehearsals, backups, reviews, compatibility checks—into the base plan when you intend to perform them. Reserve contingency for uncertainty that remains. This keeps essential safety or quality work from being squeezed out to 'save buffer.'
An example
A canary run is scheduled as normal delivery work; extra repair time if the canary exposes unexpected defects sits in contingency.
Check your result
The base plan contains the risk-reduction work you actually intend to do.
Keep this limit in mind
- Organizations use different accounting conventions; preserve the conceptual distinction even if financial labels differ.
Evidence and sources
Supports
The Green Book distinguishes prevention or mitigation costs from contingency for risks that remain after mitigation.
Organizations may use different accounting labels; the useful distinction is planned work versus allowance for residual uncertainty.
The Green Book (2026) · Optimism bias and contingency