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Published April 21, 2025 . 4 mins read

Construction Billing Methods and When to Use Each One

Before work begins on a construction project, it’s important to establish how and when the contractor will be paid. Clear payment terms reduce the risk of delays and disputes and help keep projects running on schedule. Since billing methods in construction vary depending on the type of contract, project scope, and client requirements, contractors need to understand how each one works.

Billing methods are more than administrative details—they directly impact cash flow, forecasting, and decision-making. Choosing the right billing structure for the job is key to effective construction accounting and financial planning. In this guide, we’ll cover common construction contract types and how they influence billing, as well as explore popular construction billing methods like progress and milestone billing.

Construction Contract Types and How They Relate to Billing

Lump Sum / Fixed Price

Most common among general contractors and subs alike. With a fixed-price contract, the total cost of the project is agreed upon upfront. This simplifies billing but puts the risk of cost overruns on the contractor. Best for well-defined scopes and when you can estimate accurately using job costing and historical data.

Cost Plus / Guaranteed Maximum Price (GMP)

This is popular for design-build projects or large-scale work with developers. Under it, the owner agrees to pay for actual costs plus a fee, often capped at a guaranteed maximum price. It provides flexibility but requires detailed cost tracking and transparency.

Time and Materials (T&M)

This is common among subcontractors or when the scope is uncertain. In T&M agreements, the client pays for actual labor and materials, often with a markup. This allows contractors to start work without a finalized scope, but it requires extensive tracking and can be harder to forecast.

Unit Price / Unit Cost

Frequently used in civil and infrastructure projects. Contractors are paid based on quantities of defined work units (e.g., cubic yards, linear feet). This model works well when quantities vary, but unit pricing is stable and measurable.

Construction Billing Methods

Once a contract type is selected, the billing method helps define when and how invoices are submitted throughout the job. Below are two of the most widely used methods:

Progress Billing (AIA-style)

The most popular billing method in construction.

Progress billing allows contractors to invoice monthly based on the percentage of work completed. This standardized format is often used with AIA documents and integrates well with construction accounting software.

It’s ideal for longer projects where work is billed in increments, and it promotes steady cash flow across the job lifecycle. This method ties directly to your Work-in-Progress (WIP) Report, making monitoring project health and forecasting cash flow easier. Discover the WIP Report resources center.

Best for:

• General contractors

• Multi-phase projects

• Firms using job cost tracking and WIP reporting

Advantages:

• Standardized and familiar format

• Promotes steady, predictable cash flow

• Works well with construction accounting software

Disadvantages:

• Can lead to disputes over percent complete

• Requires detailed job costing and documentation

• Accuracy is key to avoiding billing delays

Milestone Billing

Milestone billing ties payments to key deliverables or project phases rather than percent complete. Once a milestone is achieved—such as pouring the foundation or completing framing—the contractor invoices the client.

This model is often used in commercial construction or government contracts with fixed milestones built into the schedule. It offers clear checkpoints but requires that the milestones be defined and agreed upon upfront.

Best for:

• Projects with well-defined phases

• Government or institutional contracts

• When lump sum billing needs structure

Advantages:

• Clear payment structure tied to deliverables

• Reduces confusion over work progress

• Helps manage client expectations

Disadvantages:

• Delayed payments if milestones are missed

• Less flexibility than progress billing

• Requires accurate planning and scheduling

Final Thoughts on Construction Billing Methods

Choosing the right construction billing method isn’t just about how and when you get paid—it’s about setting your project up for financial success from day one. Whether working under fixed price, cost plus, or time and materials contracts, your chosen method will directly affect cash flow, forecasting, and even how your financials appear on your income statement and balance sheet.

Pairing the right billing method with sound invoicing practices can reduce delays and keep cash flowing. If late payments are hurting your bottom line, check out our blog on the top strategies for contractors to reduce payment delays.

You’ll also want to consider how your billing method affects retention, especially on longer-term projects where withheld payments can impact cash flow and working capital. If you’re not sure how these billing strategies show up in your financial statements, we’ve broken it down in plain terms to help project managers and financial leads get on the same page.

Ultimately, the more aligned your billing strategy is with project goals and cash flow needs, the more control you have over your financial outcomes. Schedule a time to see how ProNovos can simplify billings and improve job costs and cash flow visibility.