Every architecture and engineering firm manages a mix of billing models. Some clients prefer the certainty of a fixed fee, while others choose a time and materials arrangement where they pay for the hours worked.Â
Both approaches can be profitable, but they also come with different risks. Understanding how each project is performing throughout delivery helps firms protect margins and project profitability, manage scope and make better commercial decisions.
Fixed Fee vs. Time and Materials Projects: What’s the Difference?
A fixed fee project has an agreed project price set before work begins. The client knows exactly what they’ll pay, regardless of how many hours the project takes to complete. This gives clients certainty, but it also means the firm carries the financial risk. If additional time or unexpected work is required, profitability can quickly decline.
Time and materials projects work differently. Clients are charged for the actual hours worked, along with any agreed expenses or consultant costs. This provides greater flexibility when project scope changes, but accurate time recording becomes essential.
In practice, many projects use a combination of both billing models. A fixed fee might cover the design phase while variations are handled on a time and materials basis. Understanding how your firm tracks profitability across both models is where the real complexity begins.
Whatever the approach, having a single source of truth for project financial data makes it much easier to monitor performance.
How Profitability Tracking Differs by Billing Model
The way firms monitor project profitability depends on how the project is billed.
Tracking Profitability on Fixed Fee Projects
For fixed fee projects, the focus is on tracking progress against the agreed budget. Every hour worked reduces the available fee, so project managers need visibility into budgets throughout delivery rather than waiting until the project is complete.
Catching it early means there’s still an opportunity to have a scope conversation with the client, or at minimum, to understand the margin impact before it shows up in the accounts. Phase-level budget tracking is what gives project managers that visibility in time to act.
Tracking Profitability on Time and Materials Projects
For time and materials projects, the primary risk is different. Under-billing is less likely, but rate accuracy and timesheet completeness become critical.
If team members aren’t recording their time accurately, or if charge-out rates haven’t been updated to reflect actual staff costs, the billing may look healthy while the underlying margin is not. Because of this, accurate time recording is one of the most important parts of managing time and materials work.
What Metrics Should A&E Firms Track Across Billing Models?
Understanding how each billing model performs requires consistent data across a few key dimensions.
Budget vs. Actual Hours by Phase
For fixed fee work, this tells you how efficiently your team is delivering against the estimated scope. For time and materials, it tells you whether the project is progressing at the pace the client is expecting.
Charge-Out Rates and Staff Costs
Understanding the difference between what firms charge clients and what it costs to deliver the work provides a much clearer picture of project margins. Purpose-built budgeting and quoting tools make this much easier to manage across multiple projects.
Write-Offs and Write-Ons
A write-off is recorded time that won’t be billed. A write-on is a billing that exceeds recorded time. Both affect reported profitability, and tracking them separately from budget performance gives a more honest picture of how each project type performs and can help prevent project margin erosion.
Realisation Rate
Realisation measures how much recorded work becomes billed and collected revenue, and is one of the least tracked metrics across A&E. A firm might have a healthy WIP balance but a poor realisation rate, meaning much of that recorded work is being discounted or written off.Â
Project Type Comparison
Over time, firms can compare the profitability of fixed fee and time and materials projects across different project types, clients and teams. These insights help improve future pricing, quoting and project planning. Analytics and reporting tools that make this comparison easy are what turn historical data into better fee decisions on the next proposal.
Track Project Profitability with Total Synergy
Whether firms are managing fixed fee, time and materials or hybrid projects, an increased level of visibility is needed to protect margins, improve financial control and make better business decisions.
Built in Australia with support teams in Sydney and London, Total Synergy helps architecture and engineering firms manage profitability across every project, regardless of the billing model.
Budgets, timesheets, WIP and invoicing are all connected in one platform, giving project managers and principals a real-time view of project performance throughout delivery.
Book a demo today to see how your firm can get clearer visibility into project profitability across every billing model.Â
