Given that the aim of performance reviews is to improve employee performance, they should be held several times a year. A frequency of only one annual evaluation leaves too much time between feedback sessions, making it difficult to follow up on how the employee’s performance is evolving.
While there’s no one ideal frequency that applies to all industries, it’s a good idea to decide on a basic rule of thumb. For example, you can hold performance reviews once per month, quarter, season, etc.