A retirement plan that is vested allows an employee to take the contents of the plan with them when they leave the employer. Sometimes a plan is partly vested, and the amount vested is defined as a certain percentage. You can take this percentage of the plan with you if you leave your employer. However, an employee can take all of the salary that they contribute to a 401(k) plan, regardless of when they leave. They may or may not be able to take employer contributions with them.