What is Budget at Completion?

Definition

Budget at Completion (BAC) is the total approved budget allocated to a project or work package for its complete scope of work. In project cost management, BAC represents the planned cost baseline against which actual spending and performance are measured throughout the project lifecycle.

BAC remains a key reference point for project managers, controllers, and finance teams because it establishes how much the organization originally planned to spend to deliver the approved scope. It is commonly used with earned value management metrics such as planned value, earned value, actual cost, and estimate at completion.

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How Budget at Completion Works

BAC is established when the project budget is approved and the scope, schedule, resources, labor, materials, and other expected costs have been planned. The approved amounts across relevant tasks or work packages are aggregated to establish the project's total budget at completion.

For example, if a project has approved budgets of $180,000 for labor, $120,000 for materials, and $50,000 for external services, the BAC is $350,000. This amount becomes the baseline for comparing planned and actual project performance.

For procurement-related work, BAC can also guide spending decisions before commitments are made. A purchase requisition can be checked against available project budget before an approval progresses, helping finance teams maintain visibility into planned commitments.

Budget at Completion Formula

When a project budget is built from individual approved work packages, the basic calculation is:

BAC = Sum of all approved budgeted costs

Consider a project with the following approved budgets: $250,000 for labor, $175,000 for materials, $75,000 for subcontractors, and $50,000 for other project costs.

BAC = $250,000 + $175,000 + $75,000 + $50,000 = $550,000

The resulting BAC is $550,000. Actual project spending can then be compared with this baseline, while forecasts can indicate whether the expected final cost is likely to remain aligned with the approved budget.

BAC and Project Performance Measurement

BAC provides the fixed budget baseline needed to interpret project performance over time. It is different from actual cost, which represents spending incurred to date, and from estimate at completion, which represents the latest forecast of total project cost.

Percentage Of Completion can provide additional context by showing how much of the project scope has been completed. Comparing progress with spending helps finance teams determine whether project costs are tracking consistently with planned execution.

Delivery milestones can also influence financial monitoring. Delivery Completion helps establish whether a defined deliverable or obligation has been completed, while Delivery Completion Verification provides a basis for confirming completion before related financial activity is finalized.

BAC in Procurement and Spend Control

For projects with significant purchasing activity, BAC provides a reference for controlling commitments before they become actual costs. Finance and procurement teams can compare proposed sourcing decisions and requisitions with remaining project budget before approvals are completed.

For example, a purchase order for $40,000 may be reviewed against the remaining BAC allocation for a project's materials category. A real-time control such as Budget Control can monitor budget usage and trigger alerts when procurement activity approaches or exceeds defined spending thresholds.

Similarly, procurement controls can connect requisitions, approvals, purchase orders, and ERP budget information so that spending decisions remain aligned with the approved project baseline.

BAC and Forecasting Decisions

BAC provides the original baseline, while ongoing forecasts help determine whether the project is expected to finish within that baseline. When actual costs or projected remaining costs change, finance teams can compare the latest forecast with BAC to identify the size and direction of the variance.

Real-time data can strengthen this process by validating proposed commitments against current budget availability. Real-Time Budget Validation in Procurement with AI can support checks against live ERP information and multiple budget dimensions before procurement commitments are approved.

A project may have a BAC of $550,000 but a current forecast of $590,000. The $40,000 difference does not change the original BAC; instead, it signals that the expected final cost is above the approved baseline and may require management attention.

Best Practices for Managing BAC

  • Establish a clear baseline: Build BAC from approved scope, work packages, resources, and cost estimates.
  • Separate baseline from forecasts: Keep BAC distinct from actual costs and updated estimates so performance trends remain clear.
  • Monitor commitments: Track requisitions, purchase orders, and other commitments against available budget.
  • Connect progress and spending: Compare financial activity with completed project work and recognized milestones.
  • Review variances regularly: Investigate material differences between planned costs, actual spending, and forecast completion costs.

Summary

Budget at Completion establishes the total approved budget for completing a project's planned scope. It serves as a baseline for measuring financial performance, monitoring procurement commitments, evaluating cost variances, and comparing the original plan with current forecasts. Used alongside project progress and real-time budget information, BAC gives finance and project teams a consistent foundation for financial reporting and informed cost-control decisions.

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