You asked
Please provide the number of over 18 year olds who could have voted on the UK referendum to leave the EU.
We said
Thank you for your Freedom of Information request regarding the number of over 18-year-olds who could have voted in the UK referendum to leave the EU.
From our mid-2016 population estimates you can see that we estimate the number of people aged 18 and over resident in the UK on 30 June 2016 to be 51,767,543. A small number of these will have reached 18 between 23 June (the date of the referendum) and 30 June. This estimate contains people who are not eligible to vote, such as citizens of other countries living in the UK. It does not include British citizens living abroad who may eligible to vote and have registered to do so.
Of these people only British, Irish and Commonwealth citizens aged 18 or over who are resident in the UK or Gibraltar would have been eligible to vote. UK citizens resident overseas would also have been eligible to vote, provided they have been registered to vote at a UK address in the last 15 years.
Our electoral statistics collect the numbers of people who have registered to vote and you can see that on 1 December 2016, 45,766,429 (including 344,734 attainers) people were registered to vote. Some of these would have become 18 between 23 June and 1 December. This number also includes UK citizens living abroad who have registered to vote.
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Please do not hesitate to contact us directly on pop.info@ons.gov.uk if you require anything further.