You can register to vote if you are: 16 years old or over and a British citizen or an Irish, qualifying Commonwealth or European Union citizen who is resident in the UK (except for service voters or overseas voters).
Seventeen-year-olds and some 16-year olds are entitled to be included on the register as 'attainers'. They can vote once they are 18.
To qualify, Commonwealth citizens must be resident in the UK and either have leave to enter or remain in the UK or not require such leave. The definition of a 'Commonwealth citizen' includes citizens of British Crown Dependencies and British Overseas Territories.
Citizens of the European Union (who are not Commonwealth citizens or citizens of the Republic of Ireland) can vote in local elections in the UK and some referendums (based on the rules for the particular referendum), but are not able to vote in UK Parliamentary general elections. They can also vote in European elections by completing a separate application.