jorghes
LostCousins Superstar
The cut-off date is probably 2007, as that's the last year for which the GRO death indexes have been published online.
I re-read the page where I read the year 1991 again to make sure - apparently it is because the 1939 Register was continually updated until 1991, and thus those who died before 1991 have already had their records on the Register updated. Anyone who died after 1991 has to have their record "opened". You can find the post here, under the "Officially Closed Records" subheading. http://www.findmypast.com.au/1939register/1939-register-getting-started