Voters in Brighton and Hove will be asked to register about two months early this year.
The move is to ensure that the electoral roll is up to date in time for the first election of a police and crime commissioner for Sussex on Thursday 15 November.
Ian Chisnall, the independent candidate from Brighton who is standing for the post, welcomed the decision.
He said: “While this is good news, I remain concerned by the failure of the government not to hold these elections in May to coincide with local government elections as they had originally intended.
“Turnout in November is bound to be lower, due to the need for voters to visit their local polling station when the weather is much less certain and the days are shorter.
“The first Police and Crime Commissioner will need to make significant changes to the governance arrangements for Sussex Police.
“It is vital that they are elected with the largest possible mandate for this new role.
“Even though November is a long time away, I’d urge people to put the date in their diaries to remind them to use their vote”.
Brighton and Hove City Council is expected to carry out the annual canvass of electors from Monday 2 July until Monday 15 October.
The new electoral roll is expected to come into force in Tuesday 16 October.
Mr Chisnall does not yet have any official opponents.
Two Conservatives have indicated that they wish to stand.
The current police authority chairman Steve Waight may also throw his hat into the ring for the Tories.
The only Labour candidate to indicate publicly that he intends to seek his party’s nomination so far is Paul Richards, a former government adviser from Eastbourne.
The Greens and the Liberal Democrats are not expected to put up an official candidate. Mr Chisnall believes that the £5,000 deposit will unfairly put off others who might have stood as independents.