You need to be on the register to be able to vote. It may also affect your credit rating if you are not registered to vote.
Who can register?
You can register if you are 16 or over (but you cannot vote until you are 18)
A British, Irish Republic or Commonwealth citizen, a citizen of a European Union country living in the UK or a citizen of the Channel Islands or Isle of Man living in the UK. Find out if your nationality qualifies.
You need to register at the address you are living at unless you are overseas, in the armed forces or a crown servant. If you are a British citizen resident overseas or in the Armed Services or are a Crown Servant serving overseas, find out about registering to vote.
You are not automatically registered even if you pay council tax.