1930 and 1931 Electoral Registers

[Mainsforth]

Can anyone tell me either the Qualifying Date for these Registers or where I can find these Dates. 

I have a copy of the image/transcript of the page in relevant County Durham Register for my paternal grandparents and my father. Unfortunately the transcripts, unlike some for other years, do mention the Qualifying and "Coming Into Force" dates.

Thank you in advance for your help.

[arthurk]

The British Library, which holds the main national collection of electoral registers, has an online pdf guide. Most of it is a list of their holdings, but there's a very useful introduction which covers this kind of question.

The guide is called "Parliamentary Constituencies and their Registers Since 1832", and is found via a link at

https://www.bl.uk/collection-guides/uk-electoral-registers#

The section you need starts at page 20.