Bit confused about new UK road tax laws??

[JoeyBoyden1]

Basically, my road tax doesn't expire until December 1st however the new "digital era" comes into play October 1st right? Now I understand when I renew my tax, I have to do it online which I normally do anyway and this registers me however, will I have to register on October 1st even though I have tax, or just when my tax expires? Sorry if I'm in the wrong section but this new law and potential £1000 fine got me a little worries as I assumed having no road tax still comes up on ANPR anyway and that if you have road tax, it's on the PNC. Thanks for help