Who can and can’t vote in the UK at general elections?
While we think we have universal adult suffrage, this is not quite correct. You must be on the electoral register, be over the age of 18, and be a British citizen, a citizen of the Republic of Ireland or a citizen of some commonwealth countries.
You cannot vote if you are an attending member of the House of Lords, an EU citizen who is resident in the UK, if you are a convict in prison, or if you have been convicted of electoral fraud within the past five years.
Who can and can’t be a candidate in UK general elections?
This is specifically about N Ireland, though the requirements are similar elsewhere in the UK.
You must be at least 18, a British citizen, a citizen of the Republic of Ireland or of a qualifying commonwealth country, or a citizen of Malta or Cyprus.
You cannot be a candidate if you are a civil servant, as the civil service is expected to be non-political; a member of a police force or the armed forces; a judge, a member of an external parliament (except the Dáil/Oireachtas), a Lord Temporal or a Lord Spiritual sitting in the House of Lords. (In the past, if you were in the armed forces wanted out, you could apply for a release from your service if you were an election candidate. This became so popular that the rules, inevitably, were made quite restrictive.)
Certain bankrupts are disqualified, as are many convicted prisoners, or if you have been convicted of electoral fraud within the previous five years.
Being a MEP is ‘incompatible’ with being an MP. You cannot stand in more than one constituency at the same general election.
Note: the eligibility to vote and to be a candidate, and what can disqualify you from voting or being a candidate is much more complicated than this brief summary outline indicates.
These are the principles for a UK general election; for local and EU elections, the eligibility to vote is rather different. In general, EU citizens resident in the UK can vote in such elections, and may be eligible to vote in the future EU referendum.