General contracting encompasses complex project orchestration, structural engineering coordination, and multi-trade risk mitigation. In major residential remodeling and commercial construction, general contractors operate under either Fixed-Price (Lump Sum) contracts or Cost-Plus Fee arrangements. In a Cost-Plus arrangement, the contractor invoices direct project expenses (subcontractor invoices, materials, building permits) plus a negotiated **General Contractor Fee ranging between 15% and 25%** to cover project management, supervisory field oversight, insurance liability protection, and operating profit.

When presenting a fixed lump-sum estimate to a property owner, experienced contractors break down the structure into detailed CSI (Construction Specifications Institute) trade divisions (Demolition, Framing, Plumbing, Electrical, Drywall, Millwork) without exposing unit-level labor rates. Furthermore, every general contracting quotation must build in a **10% to 15% structural contingency line item** to protect projected profit margins against concealed architectural deficits uncovered during early structural demolition phases.

The absolute most critical structural component of a general contracting invoice system is rigorous **Change Order Governance**. Your estimate terms must strictly enforce: "Any deviations, substitutions, or design additions differing from the agreed engineering drawings and specifications will be executed solely upon written completion of a formal Change Order signed by Owner; all associated extra labor, parts, and administrative markups become payable in full immediately prior to commencing change work."

For substantial capital construction projects, avoid simple milestone billing in favor of formal **Percent Complete Schedule of Values (AIA G702/G703 style billing)** submitted on the 25th of each calendar month. Implement standard payment structures: **10% initial scheduling retainer, monthly draw requests based on verified engineering progress payable within 10 business days (Net-10), and a mandatory 5% to 10% retainage held by Owner until municipal Certificate of Occupancy issuance** and satisfactory punch-list completion.