A plan defined number of hours of service an employee must perform for the employer during the plan year in order to be credited with a year of service. Year of service is used for different aspects of plan administration such as eligibility for plan participation, vesting calculation and eligibility for employer contribution(s). The actual number of hours may be different for each aspect of plan administration, may not be more than 1,000 hours during any given plan year, and is defined in the plan document and the SPD.