Eligibility
FERS employees are eligible to join TSP immediately upon starting work and may join at any time thereafter. Prior to June 22, 2009, new employees had to wait at least one year before receiving matching contributions (including Agency Automatic Contributions); after this date employees were eligible for automatic contributions from day one of employment, and are immediately eligible for matching contributions once the employee begins contributing to the TSP.
CSRS employees and members of the uniformed services may join at any time.
Read more about this topic: Thrift Savings Plan