The clear expectation, as set out in the Guide to Parliamentary Work published by my office, is that Departments should ensure that Members receive a substantive response to their named day question on the date specified. However, it may not be possible for questions which are tabled for answer after the last sitting day of the Session to receive a reply.
The full ‘Guide to Parliamentary Work’ can be viewed at:
http://www.cabinetoffice.gov.uk/parliamentary-clerk-guide.aspx