After sign by witness,how long do I have to submit an application for naturalisation?

Hi

Just wonder there is a time limit to send an application away after sign by solicitor? As I still waiting a few proof of papers and maybe it will take longer than 4 weeks after signed by witness ,and if there is a time limit if is possible for me to send application away without Inis return it back and not refund the fee? Have anyone experienced this situation before? Thank you.