If you are not going to use your car, such as for an extended stay off the island, you can obtain a rebate of some of the unused road tax during your absence or delay in renewing your road tax.
Before you go away:
Or as soon as the vehicle is off the road, fill in the form TOM 12 and take it with your log book to the Department of Transport Offices or Citizen Service Centres.
You will need to nominate a location, off the road, where the vehicle will be stored during your absence, so that it can be inspected.
I have been informed of a change in procedure in that.
You should now take your bank IBAN with you, as any refund is paid directly into your account. On your return, re-tax the vehicle.
The notification cannot be backdated and is similar to the Statutory Off Road Notification (SORN) in the UK.