Most Professional Services managers or directors annually participate in the management accounting exercise of forecasting future billings and profitability. The prevalent model in experience-based Professional Services Organizations (PSO) are time and materials-based billing projects, where charges to the client are based on the actual hours consumed, typically up to a not-to-exceed number. However, the dominant model in an efficiency-based PSO is deliverable-based billing, often at a fixed price. Two distinctly different formulas are required to calculate billings and profitability across these practice areas and billing types.