Fixed price or time and materials billing?

Fixed price or time and materials – this question comes up in almost every web project, and there is no universally correct answer. Both models have their merits; which one fits depends above all on how precisely the scope can be described in advance and how much flexibility you need during the project. A well-founded choice of model is therefore part of our consulting services.

Fixed price: planning certainty with a clear scope

With a fixed price you agree a set price for a precisely described scope of services. The advantage is obvious: you know before the project starts what the implementation will cost – which makes internal approvals and budget planning easier. The flip side: a fixed price only works if the requirements are defined precisely up front. Any vagueness has to be priced in by the agency as risk, and anything outside the described scope runs through paid change requests. If many new wishes emerge during the project, the supposed cost certainty of a fixed price quickly evaporates.

Important to know: you pay for the risk buffer of a fixed price – the vaguer the requirements, the larger it has to be. A fixed price is therefore not automatically the cheaper option, but above all the more predictable one. It makes sense when it is preceded by a thorough concept phase in which scope, assumptions and acceptance criteria are recorded in writing.

Time and materials: flexibility for iterative projects

With time and materials billing you pay for the hours actually worked at agreed rates. The model is flexible: priorities can shift during the project, new insights are incorporated directly, and you only pay for work that was actually done. Transparency comes from comprehensible activity reports and regular check-ins – implemented seriously, this also includes an agreed budget frame with warning thresholds so that costs remain controllable. This model suits iteratively developed projects and the continuous evolution typical of software development.

To keep time and materials billing from becoming a black box, fixed ground rules are part of the deal: regular reports on hours worked, short coordination cycles with prioritised task lists, and an agreed ceiling beyond which further work requires consultation first. This way you stay in control of costs without giving up flexibility. The following questions help when choosing the model:

• How precisely can the scope be described? The more precise the specification, the better a fixed price fits.
• How likely are changes? If adjustments during the project are to be expected, time and materials is usually more economical.
• Do you need a fixed sum for internal approvals? Then a fixed price per project phase has a lot going for it.
• How closely do you want to steer the project? If you want to adjust priorities continuously, time and materials with a budget frame is the more flexible option.
• Are there unknowns? Legacy systems, unclear data quality or undocumented interfaces can hardly be calculated seriously at a fixed price.

In practice, a hybrid model often proves itself: clearly delimitable packages such as concept, design and the implementation of defined core features are offered at a fixed price, while parts that are hard to calculate – such as connecting a legacy system or migrating data – run on a time and materials basis with an agreed budget cap. This way you combine planning certainty with flexibility. How we structure projects into phases is shown in our project process.