You need to be on the electoral register to vote in all UK elections and referendums. You are not automatically registered even if you pay council tax.
If you receive a request for your registration information from then you are legally obliged to respond. If you do not respond you could face a fine of up to £1,000,
It is an offence to knowingly give false information and you could face a fine of up to £5,000 and/or up to six months in prison. If you do not make an application for registration when required to do so, you could face a fine of £80.
Some people also register to vote because they want to apply for credit. This is because credit reference agencies use the register to confirm where someone lives when they apply for credit in order to counteract fraud.