There is no set amount of time a person has to own a car before they can refinance. The length of time often depends on the lender.
It is recommended that a person waits at least 6 months after the original purchase before they seek refinancing. When the owner inquires into a refinance loan, it often requires a credit check. This inquiry can lower a credit score by a couple points. When a person is interested in refinancing due to high interest rates, or a hardship, they should talk to their lender. The lender can advise the person on when to refinance.