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Assumption Log – journal of assumptions and constraints in the project

03 October 2025

In project management, the Assumption Log is one of the key tools for controlling uncertainty. It helps to identify, track, and verify assumptions and constraints that may impact the project's success.
 

🧩 What is an Assumption Log?


The Assumption Log is a project document that includes:

  • Assumptions: things considered true without evidence.

  • Constraints: factors that limit the possibilities in the project.

This log is a living document that evolves with the project and is closely related to risk identification.
 

✍️ What do we record in the Assumption Log?


1. ✅ Assumptions


These are predictions we take for granted:

  • "The client will be available every Friday for progress acceptance."

  • "The project team will be available in full strength throughout the sprint."
     

📌 Their falsity can lead to delays or incorrect decisions.
 

2. 🚫 Constraints


These are factors that restrict freedom of action:

  • Budget: "The project must fit within 500,000 PLN."

  • Timeline: "The product must be deployed before the end of the quarter."

  • Technology: "The system must comply with the organization's cloud architecture."
     

📌 They cannot be ignored - they need to be designed with them in mind.
 

🔄 When and how to update?
 

  • During project initiation - the first list of assumptions.

  • During each status review - update and verification.

  • When changes occur in the project environment.
     

📍 The Assumption Log should be regularly updated - even seemingly small assumptions can turn into serious risks.
 

⚠️ Assumption Log and risk management
 

  • False assumption = potential risk.

  • Therefore, each entry in the Assumption Log should include:

    • What do we assume?

    • What could be the consequences if it doesn't hold true?

    • How do we monitor this?

 

📊 Example entry in the Assumption Log
 

ID Type Description of assumption / constraint Date Status Impact on project
A-01 Assumption Client will provide input data by 01.07 12.06 In progress High - blocks analysis
C-03 Constraint   Budget limited to 100,000 PLN 01.06 Confirmed Medium - limits features
A-05     Assumption Team will be available in full capacity 100% of the time 10.06 Outdated High - resource reallocation
 
 

🎯 Why is it worth keeping an Assumption Log?
 

  • 🛡 Reduces the risk of surprises

  • 📈 Improves planning quality

  • 📣 Facilitates communication with stakeholders

  • 🎯 Enables quick reactions to changes

mateusz.florczak.96@gmail.com

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