Late requirement changes and the scope, schedule, cost trade-off
Key Takeaway
Added scope is paid for with more cost or more time. Answer a late request with "yes, if" more budget or more time is approved, and if the budget is fixed, defer the late requirements.
Scope (what the project delivers), schedule (how long it takes) and cost (the budget) are called the triple constraints. A change to one always changes at least one of the others. When a stakeholder adds requirements after work is underway, the project absorbs the change in one of three ways: spend more money, take more time, or defer something. Knowing which constraint is fixed tells you which option is left.
What project scope is
Scope comes from requirements provided by the sponsor and key stakeholders. Scope planning is a joint effort between the project team and those key stakeholders. They must reach consensus on the requirements. The requirements must be detailed enough that no one misunderstands what the project will deliver.
Scope is the project manager's primary source of information for building the schedule and cost estimates, so any change to scope ripples into both.