Well, your first half payment is due by October 01 (and delinquent after November 03) if you only want to pay the first half.
If you do not want to pay your first half by November 03, you can also pay your full year amount by December 31. I expect that you will get a sternly-worded letter about the missing first half if you did not pay your full amount by the end of the year.
Or am I TRWTF here for reading it that way?