I think if you apply now it is active from January x
You can apply and get your code via your government gateway childcare account. Your nursery and local authority will have their own deadline for when the paperwork needs to be submitted to them - pretty sure our paperwork for September had to be done by late July, we haven't had it through for the next term yet though so anticipating it soon.
Look at the website: childcare choices. It explains it all
You should be able to apply now, it just won't apply to your nursery care until a bit later e.g. apply now and it may not be valid until Dec. I'm pretty sure its a rolling thing and the August deadline was for funding to start in September.