An assumption log template records and tracks all assumptions and constraints identified during project planning and execution, enabling active management of these hidden risk sources. According to the Project Management Institute (PMI), managing assumptions is fundamental to the Uncertainty Performance Domain in PMBOK 8 — unvalidated assumptions are a primary source of project risk that must be explicitly tracked rather than silently accepted. The assumption log template transforms implicit premises into explicitly managed items with owners, validation methods, and impact assessments that are reviewed regularly throughout the project. Projects that do not maintain an assumption log template typically discover failed assumptions through project failures rather than through proactive validation, resulting in expensive course corrections that could have been prevented.

What is an Assumption Log?

An assumption log template is a dynamic project document that captures every assumption made during project planning, identifies who owns validation, tracks validation status, and records the impact and response if an assumption proves false. It transforms the implicit risk of assumed conditions into explicitly managed project risks with defined owners and validation schedules. The assumption log is distinct from the risk register in that it focuses specifically on premises accepted as true during planning rather than on identified risk events. However, when an assumption is refuted — confirmed to be false — it typically becomes an entry in the risk register or triggers a change request. In PMBOK 8, the assumption log template is maintained throughout the project lifecycle and is reviewed at each risk review session, phase gate, and project status meeting to ensure no failed assumption goes undetected long enough to cause significant project harm.

What's Included in This Assumption Log Template?

• Assumption ID and Description — Unique identifier and clear, specific statement of each assumption in testable terms that enable unambiguous determination of whether the assumption has been confirmed or refuted through validation activities.
• Category Classification — Type of assumption (technical, business, resource, external, regulatory, environmental) that enables category-level trend analysis and targeted review during risk identification sessions focused on specific risk domains.
• Validation Method — The specific approach that will be used to confirm or refute the assumption, including who will perform the validation, what data or evidence will be examined, and when the validation activity will be completed relative to the project schedule.
• Validation Status — Current status of each assumption (Confirmed, Refuted, Pending Validation, Validation Overdue, Not Yet Validated) providing an at-a-glance view of assumption validation progress and identifying overdue items requiring immediate attention.
• Impact if False — Assessed consequence to project scope, schedule, cost, or quality if the assumption proves to be incorrect, prioritizing validation efforts toward the assumptions whose failure would cause the greatest project harm.
• Owner and Validation Due Date — Responsible person for validating the assumption and the target date by which validation must be completed, creating accountability and enabling proactive follow-up for overdue validation activities.
• Response if Refuted — Pre-planned response action if the assumption is confirmed false, reducing reaction time when validations fail by having a preliminary response strategy ready before the assumption is actually tested.

How to Use This Assumption Log Template (PMBOK 8)

1. Populate during planning with all known assumptions — Document every assumption made during planning activities including all statements like "we assume...", "assuming...", or "provided that..." captured in discussions, workshops, and planning documents. The comprehensive initial capture is the most important step.
2. Assign a validation owner and due date for every assumption — Every assumption must have a named owner responsible for validating it and a target date by which validation must occur. Assumptions without owners are never validated regardless of how clearly they are documented.
3. Review the log at each project status meeting — Include assumption log review as a standing agenda item at all project status meetings to check validation progress, escalate overdue validations, and discuss implications of any recently refuted assumptions.
4. Convert refuted assumptions into risk register entries — When an assumption is confirmed false, immediately create a risk register entry or change request to formalize the impact assessment and response planning. Do not leave refuted assumptions only in the assumption log without escalation.
5. Archive the completed log at project closure — Submit the final assumption log as part of lessons learned, documenting which assumptions proved accurate, which were refuted, and what the actual impacts were — information that improves future project planning accuracy.

When to Create This Document (PMBOK 8)

The assumption log template is created during the Planning Performance Domain, alongside the risk management plan and risk identification activities. In PMBOK 8, the assumption log is a required project document that is maintained throughout the lifecycle and reviewed as part of every risk management process. Initial population occurs during planning workshops and is updated whenever new assumptions are identified or existing assumptions reach their validation dates.

Related Templates

• Risk Management Plan Template
• Risk Report Template
• Project Documents Register Template
• Change Request Template
• Lessons Learned Template