Verification and validation are one of a project’s largest costs. Rework is the only cost larger than verification and validation in a project. If it is not adequately planned, not only will the schedule have to be extended but the overall cost of doing validation and verification will increase.

A lot of this can be avoided by well thought out requirements taking into account factors such as if the requirement is verifiable, what constitutes as proof of it being verified, and the primary method used to verify that requirement. Moreover, who is verifying the requirements, who where and when system validation will be done and the interfaces involved must also be planned.

This well thought out planning is necessary to avoid the company losing time, and more importantly money. The below source goes more into detail on how to perfect the planning of the V&V process and how to prevent this from happening.

Source: Thinking Ahead to Verification and Validation by Louis S. Wheatcraft