The Electoral Commission informs me that there is no requirement for returning officers to record the number of postal ballot packs received in any period before the close of poll. Returning officers are required to report the number of postal ballot packs returned in the 25 days after the close of poll, including those which were deemed undeliverable by the Royal Mail, and the latest figures are available on the Commission website at:
www.electoralcommission.org.uk
Returning officers are not required to provide information relating solely to the period of 24 hours after close of poll.