02.3
Forecast credibility
Does the forecast reflect what is now known, or does it reflect what was committed?
What goes wrong without it
A forecast that never moves is not stable, it is unexamined. Programmes routinely hold a forecast at the approved figure until the evidence becomes undeniable, at which point the whole variance appears in one period and is reported as a sudden deterioration. It was not sudden. The information existed and the forecast was not permitted to carry it.
What to examine
- Plot the forecast over time. A flat line followed by a step is the signature of a suppressed forecast, not a well-controlled one.
- Check whether known risks that have already materialised are in the forecast or still in the risk register.
- Establish who is permitted to move the forecast, and whether that person reports to whoever is accountable for the number.
- Test contingency drawdown against progress. Contingency consumed faster than scope completed is an early and legible warning.
Required by
- AACE International Recommended Practice 56R-08 and 18R-97 on estimate classification and expected accuracy.
- PMBOK Guide, Eighth Edition, November 2025, finance performance domain.
- ISO 21502:2020, Clause 7, cost management practice.
Read the sources
- AACE International RP 56R-08, cost estimate classification for building and general construction, rev. 7 August 2020rev. 7 August 2020; read 2026-09-05.A five-page sample of the 21-page RP, published free. It carries Table 1 (the classification matrix with the accuracy ranges) and the paragraphs that qualify it. The deliverables maturity matrix that determines the class, Table 3, is not among the sample pages. Until 5 September 2026 this entry called the sample a table of contents, which it is not.
- ISO 21502:2020, guidance on project management2020; read 2026-09-26.The link carries the abstract and publication details, not the guidance text.
In the asset lifecycle method
The steps of the two methods that this domain examines.