DVLA will send you a V11 reminder as normal approximately 2 weeks before the tax is due to expire.
You can then apply online or at the post office as normal or declare SORN if the vehicle is off the road.
Well there is still a chance that your car was built in the previous year, and DVLA accommodate this situation also.
DVLA will accept a dating certificate from BMIHT Gaydon, which shows the actual date of manufacture from the archived Rover production records as evidence that the car was made in the previous year.
In the table I have carefully avoided referencing registration suffixes because the legislation is based on date of manufacture not on the date of first registration.