Money an employer pays into a retirement plan is not always the employee's to keep immediately. Vesting rules determine when it becomes irrevocably theirs.
Employee and employer money are treated differently
Contributions taken from an employee's own salary belong to that employee from the moment they are made, and no length of service affects them.
Employer contributions are a separate matter. The plan can require a period of service before the employee acquires an unconditional right to them.
Until that condition is met, the money sits in the account and is invested, but leaving the job forfeits the unvested portion back to the plan.
Cliff and graded schedules work differently
A cliff schedule vests nothing until a defined service milestone, at which point the entire employer balance becomes the employee's at once.
A graded schedule vests a rising share year by year, so departing partway through preserves a proportion rather than nothing.
The distinction has large consequences for someone considering a move, since leaving shortly before a cliff forfeits everything that a graded plan would have retained.
The purpose is retention and cost recovery
Hiring and training carry real costs that are recovered only if the employee stays long enough to become productive.
Vesting converts part of the compensation package into a reason to remain, without requiring a contract that binds the employee directly.
It also reduces the cost of high turnover, since forfeited contributions can offset future employer contributions or plan expenses depending on the rules.
The effect is strongest in roles where replacement is expensive and weakest where employees leave for reasons unrelated to compensation, which is why schedules vary between industries.
Vesting is not the same as availability
Becoming vested means the money is owned. It does not mean it can be spent, since retirement plans separately restrict withdrawals before a qualifying age.
Leaving an employer usually allows a vested balance to be transferred to another plan or an individual account, keeping its tax treatment intact.
Cashing out instead typically triggers tax and penalties, which is why transferring is the default recommendation in most systems.
Small balances are sometimes an exception, since plans may be permitted to force out accounts below a threshold rather than administer them indefinitely.
What to check before changing jobs
Plan documents state the schedule and how service is counted, and the counting method matters as much as the number of years required.
Some plans measure by plan year and others by anniversary date, which can shift a vesting milestone by months in either direction.
Rules on vesting, transfers and early withdrawal differ substantially by country and change over time, so the governing plan document is the only reliable source.