Before the ERISA law was passed, workers who left the labor force lost credit for all vesting time credited for previous work. Today, you will have a break in service if you do not complete at least 501 hours of work with your employer in one year. If you are vested, even partially under a graduated vesting schedule and return to your job, you must be given credit for prior service, regardless of how long the break lasts. If you are un-vested (not vested) and stay away from a job for five consecutive years, you may lose all the years you have toward vesting under the plan, even if you return to the same employer. By law, your employer cannot consider a one-year maternity leave as a break in service.