According to the PMBOK® Guide, the Cost Baseline is the specific version of the time-phased project budget that excludes management reserves. It is the primary output of the Determine Budget process.

The Process Logic:

Estimate Costs: In this preceding process, the project manager develops an approximation of the monetary resources needed for each individual activity or work package.

Determine Budget: The project manager aggregates the estimated costs of individual activities or work packages to establish an authorized cost baseline.

Components of the Cost Baseline: The baseline includes all authorized budgets for the work packages and planning packages, plus contingency reserves (for " known-unknowns " ).

Difference from Total Project Budget: The Cost Baseline plus the Management Reserve (for " unknown-unknowns " ) equals the Total Project Budget. While the project manager can typically authorize the use of contingency reserves, the management reserve often requires a formal change request for access.

Performance Measurement: Once established, the cost baseline is used as a basis for comparison to actual results. It is typically displayed as an S-curve, showing the cumulative costs over the project ' s duration.

Analysis of Other Options:

A. Estimate Costs: This process produces Activity Cost Estimates and the Basis of Estimates. It is the " input " to the Determine Budget process, but it does not yet produce the consolidated, time-phased baseline.

B. Control Schedule: This is part of the Schedule Management knowledge area, not Cost Management. Its purpose is to monitor the status of the project to update project progress and manage changes to the schedule baseline.

D. Develop Project Charter: This process occurs during the Initiation phase. While it may include a " high-level summary budget " or " pre-approved financial resources, " it does not contain the detailed, decomposed cost baseline required for project execution.