Which fee structure ensures the designer cannot exceed a fixed amount?

A lump sum fee structure is the correct choice because it establishes a predetermined total amount that the client agrees to pay for the entire scope of work outlined in the contract. This fixed fee provides a clear budget for both the client and the designer, ensuring that the designer cannot charge more than this agreed amount, regardless of the hours spent or resources used during the project.

This structure is particularly beneficial as it encourages the designer to work efficiently and manage the project within the specified budget, fostering accountability and clear expectations. Clients often prefer lump sum agreements for their predictability, as they know upfront the maximum financial commitment.

In contrast, hourly rates charge clients based on the time spent by the designer, leaving the total cost uncertain and potentially exceeding the client's initial budget. Percentage of profit and cost-plus structures also introduce variables based on the overall costs of the project and the designer’s profit margin, which means there are no fixed amounts. Thus, these alternatives do not guarantee a capped expenditure like the lump sum does.