I don't know the exact grace period, but this year I renewed my car registration 20 days after it had expired, and no one gave me any grief. However, I would worry more about the insurance -- in Dubai, where I perviously lived, insurance companies normally gave a 13 month policy, effectively giving you a grace period of one month to renew -- but in Qatar, insurance policies are for 12 months only (at least, that has been my experience with two different insurance companies). So if you are driving around with expired registration, you are also driving around uninsured. If there is an accident, that could create far bigger problems for you than any fine for delayed registraton.
