This information is provided in your Plan Documents. If Sentinel provides these documents for you, you can obtain a copy of your Summary Plan Description (SPD) from the reporting section in your plan sponsor web account. Access it by choosing "Statements, Forms & Reports" on the top bar and the sub-option "Reports & Forms", then select “View Reports & Forms” from the drop-down menu. Your SPD provides pertinent information regarding the operation of your retirement plan, including the participation requirements for your employees.