Accurate determination of project cash flow is vital for contractors in construction projects. Among cash flows, the contractor’s cash ouflow is particularly important, and neglecting it can lead to liquidity shortages during the project. With the advancement of modern computational tools, especially Building Information Modeling (BIM) in the construction industry, the contractor’s cash ouflow can be calculated at any moment of the project easily and within minutes. This paper presents a framework based on contractors’ payment models for labor, equipment, and materials, which was implemented in a real construction project. The model is designed with an emphasis on the time lag between resource utilization and cost payment, and the actual cash flow is compared with the total cost curve. The results indicate that the primary source of discrepancy between the total cost curve and the outflow cash flow is the time difference between recording costs and actual payments. This delay creates liquidity peaks in capital-intensive and discrete costs such as materials, while continuous costs, such as labor, only cause minor temporal variations. Using the total cost curve to estimate profitability introduces a limited error of approximately 0.3 to 2.1%. However, the contractor’s actual cash requirement due to delays in material payments can be overestimated by up to 64%, whereas labor payments mainly cause only minor shifts in cash flow. Therefore, active management of material payments and negotiation with suppliers can reduce liquidity risk and improve financial decision-making.