Phase sign-off is the formal verification that each phase of construction meets quality standards before the next trade begins work that would cover or be affected by the previous phase. The economic rationale: a framing deficiency corrected during framing costs hours and a small amount of lumber. The same deficiency corrected after drywall requires drywall removal, framing correction, drywall replacement, taping, texturing, and painting — multiplying the cost by 8–15×. After paint: add repainting. After occupancy: the full correction cost plus client relationship damage. Phase sign-off produces signed checklists confirming prior phase quality before the next trade begins — making the sign-off party accountable for their work’s condition at handoff and ensuring problems are caught at the cheapest possible correction point rather than accumulated to the punch list.