Full 100% vesting after X years of service, with no gradation of vesting before that time. Benefits must be 100% vested after five years. If participants leave the company or terminate prior to the vesting date, no partial benefits are received. efined Benefit Plan — Any plan that is not an individual account plan, and is designated primarily for retirement. The employer's contributions are determined actuarially. The formula may provide a flat monthly payment; or it may provide a definite amount for each year of service, expressed either as a percentage of compensation for each year of service or as a flat dollar amount for each year of service.