Insurance Grace Period After Buying A Car. Most car insurance companies provide a grace period for premium payments. You only have a grace period of around 20 days, depending on the state, to register.
If you have an existing car insurance policy, there are two common grace periods for getting insurance on a new car: Without insurance, your new car can't be driven off the lot or registered. Talk to your specific insurer if you want to know their specific policy on a grace period.