Unless that voucher date is for the Essay Exam, you have no worries.
For the assignment there is no deadline. The date you see on that voucher means nothing.
However, if it is a voucher for the Essay Exam , then yes you would have to take the essay by then. But it is not for the Essay Exam, because I don't know of anyone who would wait to take it after they have uploaded their assignment.
So don't worry.
Mark