Understanding the 5 Types of Consulting and Professional Service Projects

Lauri Eurén

Exploring Different Types of Professional Service Projects

In professional services, there are various different ways to structure projects and invoicing. The types of projects you sell, have a large impact on how your business should be run: how resources are allocated, which types of competencies you need to hire etc. Understanding these different project types can help you make the best decision for your needs and ensure successful collaborations with your clients. Let's explore the most common types of consulting and professional service projects: Time and Materials, Fixed Price, Target Price, Retainers, and Success Fee projects.

Selling huge fixed price implementations with large teams is a very different business from delivering smaller retainer-based projects. Often, the type of professional services company you are, partly dictates the types of projects you're able to sell. IT consultancies often sell full-time-equivalent consultants with a time and materials model, or engage in large build projects with a fixed or target price model.

Typically, marketing agencies are selling their work retainer-based. What many people don't realize, is that the types of projects you sell is not set in stone. You could sell your work retainer-based in IT consulting, or sell time & materials consulting even if you're a marketing agency. Understanding the nuances between the different models will help you steer your business to the right direction.

Time and Materials Projects

Time and Materials (T&M) projects are straightforward and flexible, making them a popular choice for many consulting engagements. In this model, you pay for the actual time spent by the consultant and any materials used. In a typical consulting project, there's no materials, but simply the time that the consultant uses that's being billed for. This approach is particularly useful when the project scope is not fully defined or may evolve over time. Many times staff augmentation roles are sold like this, as the consultant joins the client team, and there's no specific project that's being scoped. Bigger projects can also be sold with a T&M invoicing, but often the client wants the consultant to also share the risk.


  • Flexibility: You can adjust the project scope as needed without renegotiating terms.
  • Transparency: You only pay for the actual work done, with detailed timesheets and expense reports.


  • Budget Management: Costs can become unpredictable if the project scope expands. Requires active communication and trust between you and the client.
  • Oversight: Requires regular monitoring to ensure efficiency and avoid scope creep.

Fixed Price Projects

A Fixed Price project involves a set price agreed upon before the work begins. This model is ideal when the project scope is well-defined and unlikely to change. However, even if the project scope seems like unlikely to change, there's a high chance it will. Focus on creating clear change management process for these situations.


  • Predictability: You know the total cost upfront, making budgeting easier.
  • Risk Management: The consultant assumes the risk for any cost overruns.


  • Scope Definition: Requires a detailed and accurate project scope to avoid misunderstandings.
  • Flexibility: Limited ability to adjust the project scope without renegotiating the contract.

Target Price Projects

Target Price projects combine elements of both T&M and Fixed Price models. The client and consultant agree on a target price, but the final cost can vary within an agreed range based on actual performance and outcomes. This is a good way to agree on a budget, but still share risk for any possible cost overruns.


  • Balanced Risk: Both parties share the risks and rewards, making this a fair way to run projects.
  • Incentives: Encourages consultants to deliver efficient and high-quality work.


  • Complexity: Requires clear agreements on performance metrics and cost adjustments.
  • Monitoring: Needs careful tracking to ensure alignment with target objectives, similarly as in the fixed price model.


A Retainer arrangement involves paying a consultant a regular, predetermined fee (monthly, quarterly, etc.) for a defined set of services or availability over a specified period. Some retainers might involve a fixed amount of work every month, while some are structured outcome-based, regardless of the actual workload that the consultant uses. In some cases, when there's an agreed monthly workload, the consultant keeps track of the total working hours over time. If there's more work one month, perhaps the next month, it's possible to work a bit less.


  • Consistency: Ensures continuous access to the consultant's expertise.
  • Predictability: Easier to forecast your business revenue-wise as fixed amount of money comes in every month.


  • Commitment: Requires a longer-term financial commitment.
  • Utilization: Important to ensure you get full value from the retainer agreement. It's easy to work more than agreed every month.

Success Fee Projects

Success Fee projects, also known as contingency fee projects, involve paying the consultant based on achieving specific outcomes or performance targets. This model is common in areas like sales consulting or M&A projects for management consultants, where the fee is tied to results.


  • Alignment: Consultant's incentives are directly aligned with your business goals.
  • Risk Mitigation: You only pay if the desired outcomes are achieved.


  • Outcome Definition: Requires clear and measurable success criteria.
  • Negotiation: May involve higher fees to compensate for the consultant's risk.


Choosing the right type of consulting or professional service project depends on your specific needs, the nature of the work, and your risk tolerance. Time and Materials projects offer flexibility, Fixed Price projects provide cost certainty, Target Price projects balance risk and reward, Retainers ensure consistent access to expertise, and Success Fee projects align incentives with outcomes. By understanding these options, you can make informed decisions that support your business. Perhaps you'd like to take your business to another direction, moving from a retainer model towards T&M invoicing, or larger implementation projects with a target price model. Choosing the project type will greatly shape the way you do business, so weigh the upsides and downsides carefully.

Lauri Eurén

Lauri Eurén is the CEO & Founder of Operating - a former consulting professional with experience from hands-on consulting as well as leading an agency operation.


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