You are covered from the date you selected the NUCO insurance, once you have a confirmed booking, until the date you get home.
There are two areas of cover within the policy, cancellation cover then everything else.
Cancellation cover is valid from the time you are accepted for cover, this is when you added the insurance to your booking and will end when you leave your home and start your holiday. There is always the possibility that something unexpected may happen and you need to cancel your booking, this could be covered by your insurance. Please see the cancellation section of the insurance policy to see what is and what isn't covered. You can find both the standard and superior policies here.
For all other sections of the group policy, the insurance will start when you leave your home to start your journey and ends on your return to your home on completion of the holiday. Depending on the policy you have, standard or superior, this may cover emergency medical treatment, missed departure, baggage etc, please check the specifics on the policies and statement of insurance.
Travel insurance cannot be purchased if you have started your holiday.