
The quick answer is "anyone not already on the electoral register". It is now too late to register to vote. There are also people who cannot vote in General Elections.
- members of the House of Lords (although they can vote at elections to local authorities, devolved legislatures and the European Parliament)
- EU citizens resident in the UK (although they can vote at elections to local authorities, devolved legislatures and the European Parliament)
- anyone other than British, Irish and qualifying Commonwealth citizens
- convicted persons detained in pursuance of their sentences (though remand prisoners, unconvicted prisoners and civil prisoners can vote if they are on the electoral register)
- anyone found guilty within the previous five years of corrupt or illegal practices in connection with an election