The 12-month policy will generally start on the date that the last car insurance is up for renewal, with short-term cover used to protect the other cars in the interim. For example, if you have one car that needs to be insured from February and another in June, the February car will be insured first but the policy will actually renew in June when both cars are covered. After the last car has been insured for a full 12 months, the policy will renew each year until you choose another policy.
The insurance certificate or cover note issued by the insurance company constitutes the only legal evidence that the policy to which the certificate relates satisfies the requirements of the relevant law applicable in Great Britain, Northern Ireland, the Isle of Man, the Island of Guernsey, the Island of Jersey and the Island of Alderney. The Act states that an authorised person, such as a police officer, may require a driver to produce an insurance certificate for inspection. If the driver cannot show the document immediately on request, and evidence of insurance cannot be found by other means such as the MID, then the Police are empowered to seize the vehicle instantly.
If the younger driver is covering his own costs, it might be cheaper for him to take out his own policy but include one of the older, lower risk drivers from the household as a named driver (as long as the older drive will use the car). However, if the older driver is footing the bill for both policies, multi-car insurance may still work out cheaper.
Several jurisdictions have experimented with a "pay-as-you-drive" insurance plan which utilizes either a tracking device in the vehicle or vehicle diagnostics. This would address issues of uninsured motorists by providing additional options and also charge based on the miles (kilometers) driven, which could theoretically increase the efficiency of the insurance, through streamlined collection.