When you roll over a retirement plan distribution, you generally don’t pay tax on it until you withdraw it from the new plan. By rolling over, you’re saving for your future and your money continues to grow tax-deferred.
If you don’t roll over your payment, it will be taxable (other than qualified Roth distributions and any amounts already taxed) and you may also be subject to additional tax unless you’re eligible for one of the exceptions to the 10% additional tax on early distributions.