While almost every project has a cost and budget, project billing only comes into play when you have a paying customer. At Birdview PSA, we define project revenue, or billing, as the total amount of money a customer pays for a project.
Similar to cost, revenue can be represented through several financial metrics:
- Target Revenue
The expected total amount the customer will pay for the project. For a flat-fee project, Target Revenue is equal to the Project Fixed Fee. For a Time & Material project, it should reflect the amount you expect to collect while still achieving the required profit. - Actual Billing
The amount associated with work that is ready to be billed. It includes actual billable time multiplied by the applicable billing rates, billable expenses, and flat fees for completed activities. Ideally, final Actual Billing should equal or exceed Target Revenue. - Estimate at Completion (EAC) Project Billing
The sum of Actual Billing and the expected billing for all remaining labor, planned billable expenses, and flat fees for unfinished activities. Ideally, Revenue Variance, the difference between Target Revenue and EAC Project Revenue, should be zero or positive.
Project billing is more than simply sending invoices. It is an end-to-end process that starts with estimating revenue, continues through time and expense tracking, and ends with payment collection and profitability analysis.
What is project profit?
Project profit represents the financial value remaining after all project costs have been deducted from project revenue.
Naturally, the goal is to collect more revenue from the customer than it costs to complete the project.
Profit can be measured at different stages of the project lifecycle:
- Target Project Profit
The expected difference between Project Revenue and Project Cost at project completion. It can be tracked as an absolute amount or as a percentage, usually referred to as Profit Margin. - Actual Project Profit
The real-time difference between Actual Project Revenue and Actual Project Cost. - Estimate at Completion (EAC) Project Profit
The difference between forecasted project revenue and forecasted project cost at completion.
Project profitability depends on understanding the relationship between revenue, project costs, and profit. Monitoring these metrics together helps organizations evaluate financial performance and identify opportunities to improve margins.
Project billing types compared
Choosing the right project billing model depends on the project scope, level of uncertainty, client relationship, and how work will be delivered. The table below compares the most common billing types used by professional services organizations.
| Billing type | Best for | Advantages | Challenges |
|---|---|---|---|
| Flat Fee | Projects with a clearly defined scope, timeline, and set of deliverables | Provides predictable pricing for the client and predictable revenue for the service provider | Scope changes, underestimated effort, or rising costs can reduce project profitability |
| Time & Material | Projects with evolving requirements, uncertain scope, or changing resource needs | Allows teams to bill for actual hours worked and approved expenses | Final costs are less predictable for clients and require accurate time and expense tracking |
| Milestone Billing | Projects delivered in defined phases or tied to specific outcomes | Aligns payments with visible progress and supports more predictable cash flow | Milestones and acceptance criteria must be clearly defined to avoid disputes or payment delays |
| Retainer | Ongoing services, long-term client relationships, and recurring support work | Creates recurring revenue for the provider and predictable costs for the client | The service scope, included hours, rollover rules, and overage charges must be managed carefully |
| Performance-Based | Projects where fees can be tied to measurable business outcomes or performance targets | Aligns provider incentives with client results and may create opportunities for higher revenue | Success criteria, measurement methods, external dependencies, and payment triggers must be agreed in advance |
While each billing model has its own advantages, the right choice depends on project scope, pricing strategy, client expectations, and the level of flexibility required. Many organizations use different billing models for different clients or combine multiple approaches across their project portfolio.
How billing rates are applied
Time & Material projects can use different billing rates depending on the customer, project, activity, resource, or role. Understanding how these rates are applied helps teams price work consistently and generate accurate invoices.
Resource Hourly Rate
The billing amount is calculated using the hourly rate assigned to an individual employee, regardless of which project they are working on.
Project Hourly Rate
The same hourly billing rate is used for the entire project, regardless of which team member performs the work.
Customer Hourly Rate
All projects completed for a particular customer use the same billing rate, regardless of the resource performing the work.
Activity Hourly Rate
Billing is based on the rate assigned to individual project activities or tasks. This approach can combine hourly work with fixed-cost activities.
Rate Cards
Rate cards provide the most flexibility for complex billing arrangements. Rates can vary by project, person, role, service, or customer. For example, the same employee may work as a designer at one rate in one project and as a senior design lead at a different rate in another.
Accurate time tracking is essential for maximizing billable hours and ensuring customers are charged correctly. It also allows teams to monitor total project effort, manage schedules, and identify potential budget overruns in real time.
Before selecting a billing type or setting billing rates, determine the expected income required to:
- Pay bills and taxes
- Cover project and operating costs
- Pay employee and contractor compensation
- Generate the required profit
Payments and billing schedules
Once the billing model has been agreed with the customer, the next step is to define when and how much the customer will pay. Payment schedules vary by project, but fixed-fee projects commonly use installments tied to major delivery stages.
Many fixed-price projects divide payments across multiple milestones rather than invoicing the entire amount at once. Milestone billing helps improve cash flow while linking payments to visible project progress.
For example, 25% of the project fee may be billed when the contract is signed, 50% when the working prototype is delivered, and the remaining 25% when user acceptance testing is completed. Time & Material engagements may instead use recurring weekly, bi-weekly, or monthly invoices.
Managers should compare planned payments with actual invoices and payments to understand what is outstanding, when the next payment is expected, and whether billing is progressing according to the agreed schedule.
Project Billing Dashboard
A centralized billing dashboard gives project managers and finance teams real-time visibility into invoice status, billed amounts, payment progress, and outstanding balances.
Advanced project billing arrangements
Advanced billing arrangements adapt to the specific needs of both the client and the service provider.
Performance-based billing
The provider earns more when predefined performance goals or business outcomes are achieved. This model aligns the provider‘s incentives with the customer‘s results, but success criteria and measurement methods must be clearly defined.
Milestone billing
Payments are linked to the completion of specific phases, deliverables, or acceptance points. This creates transparency and allows clients to pay for visible progress.
Retainers
The customer pays a recurring amount for a defined bundle of services, hours, or ongoing support. Retainers create predictable revenue for the provider and predictable costs for the client.
The appropriate model depends on scope stability, project duration, client expectations, and whether payment should be tied to effort, delivery stages, recurring services, or measurable outcomes.
Whatever billing arrangement is selected, both parties should agree on the scope, rates, milestones, acceptance criteria, payment triggers, and change process before work begins. Clearly documented terms reduce disputes and create a stronger foundation for the client relationship.
Client communication and billing agreements
Effective communication about billing establishes clear expectations from the beginning of the project. Rates, billing schedules, payment methods, included services, and acceptance criteria should be documented in straightforward language that both parties understand.
If billing terms need to change as the project progresses, inform the customer promptly, obtain approval, and document the revised agreement. This helps maintain an accurate record and reduces the risk of disputes later.
Clear and consistent communication creates transparency, strengthens trust, and gives both the customer and the service provider a shared understanding of how project charges will be calculated and invoiced.
Billing reporting and analytics
Billing reports help organizations monitor outstanding invoices, forecast future revenue, analyze profitability, and identify billing issues before they affect cash flow. Regular reporting also supports better pricing, staffing, and project management decisions.
Common project billing reports
Project billing reports help organizations monitor revenue, invoice status, profitability, and payment performance throughout the project lifecycle. Together, these reports provide the visibility needed to improve cash flow, identify billing issues early, and make informed financial decisions.
| Report | Purpose | Typical users |
|---|---|---|
| Invoice Status Report | Tracks draft, sent, paid, overdue, and outstanding invoices to monitor billing progress and cash flow. | Finance teams, Project Managers |
| Revenue Forecast Report | Forecasts future revenue based on planned work, scheduled billing, and project progress. | Executives, Finance, PMO |
| Project Profitability Report | Compares project revenue, costs, and profit margins to identify the most and least profitable engagements. | Executives, Finance, Project Managers |
| Budget vs. Actual Report | Compares planned budgets with actual project costs and billable revenue to identify budget variances. | Project Managers, Finance |
| Accounts Receivable (A/R) Aging Report | Identifies overdue invoices and outstanding customer balances to support collections and improve cash flow. | Finance teams, Controllers |
| Billing Rate Analysis Report | Evaluates billing rates across resources, projects, customers, and services to improve pricing decisions. | Finance, Operations, Sales |
| Unbilled Time & Expenses Report | Highlights completed billable work that has not yet been invoiced, helping reduce revenue leakage. | Finance teams, Project Managers |
Project billing and client retention
Good billing practices improve client satisfaction while supporting healthier cash flow and stronger long-term relationships.
- Clarity and transparency: Explain billing terms from the beginning and provide invoices that clearly show what the customer is being charged for.
- Timely invoicing: Send invoices as soon as work is completed or according to the agreed billing schedule.
- Flexible payment options: Offer appropriate payment methods and terms where operationally practical.
- Prompt responses: Answer client questions about invoices quickly and accurately.
- Consistent invoice formatting: Use the same structure across invoices so customers can easily find important information.
- Professional follow-up: Send polite reminders when payments become overdue.
- Feedback: Ask clients whether the billing process is clear and convenient, then use their feedback to improve it.
Client-friendly billing practices do more than encourage timely payment. They reduce confusion, build trust, and create a stronger foundation for recurring business.
Software and tools integration
Integrating billing with project management, accounting, CRM, and reporting systems eliminates duplicate data entry and creates a single source of truth for project finances.
When billing systems connect with operational and financial tools, project information, customer records, time entries, expenses, invoices, and payments can move between systems without repeated manual input. This reduces errors and keeps financial records more accurate.
Look for billing software that connects with the project management, accounting, and CRM applications already used by your organization. A connected system allows teams to monitor project progress, budget status, customer details, and billing performance without constantly switching between tools.
Centralizing this data saves administrative time and gives organizations a more complete view of project delivery and financial performance. Managers can see how project progress, resource usage, billing, revenue, and customer outcomes connect, supporting faster and more informed decisions.
