There are two ways you can buy road tax:
You can apply for it on the DVLA website providing the Motor Insurance database (MID) has been updated with your new insurance details. This way you don’t need to print your car insurance certificate or go to the Post Office. Please make sure that you have your car insurance policy number to hand. You can find it in your My account > "My policies" section.
In order to buy your road tax at a Post Office you’ll need to print your car insurance certificate in colour using a high quality paper. You can find your car insurance certificate in your My account > "My policies" section > View Documents.
You can access your insurance certificate via My account at any time.