Polling Procedure
A person may only cast a vote if he/she is on the Electoral Register - even if he/she would otherwise qualify to vote. If, because of a clerical error, an elector's name has been left off the Electoral Register, the Electoral Registration Officer can amend the Register up to 9pm on polling day. Because the franchise between electors varies (for example, EU citizens who are not Commonwealth or Irish citizens cannot vote in UK Parliamentary elections), ballot papers are only issued after checking the marker in the Electoral Register before an elector's name which helps to identify which elections the individual is eligible to vote in.
Votes can be cast either in person at a polling station, by post or by proxy. British citizens residing abroad and registered as overseas electors cannot vote at British high commissions, embassies or consulates - their votes can only be cast either in person in the constituency where they are enrolled in the United Kingdom, by proxy (who must reside in and be eligible to vote in the UK) or by post (although this option is less popular as postal ballot packs are only despatched by returning officers at 5pm 11 working days before polling day at the earliest and must be received by the returning officer by the close of poll to be counted).
Read more about this topic: Elections In England