Time & Materials model is particularly useful in contexts where the project is complex and the requirements are not clear up front. Or, if it's prone to specification and design changes mid-stream.

This engagement demands flexibility. It requires us to adapt midstream change requests with the design and development.

It gives you greater flexibility in terms of developing the solution specification on an ongoing basis; and modifying the specifications based on the changing business and market needs.

This is a resource-based model, where the cost is directly related to the total number of resources deployed in the project and the time spent by them.