Mine was due end of May, it's been extended until end of November.
Same with me, 30th May extended to 30th November, Google 'check if car is taxed', that'll take you to the government website, don't use any of the others, that will show you if you have the 6 month extension although it will not update it until the current MOT runs out as there are currently talks of ending the scheme. Anyone already granted the extension will be ok, it will not be withdrawn.