Your many similar posts suggest that you're in India (or, at least, on the Indian sub-continent). You need to be aware that there are many differences between 'British English' and 'Asian English', so the suggestions you get from people here in the UK might not necessarily be exactly what's required in your own country. However here's how I'd word the email:
"Dear ____
I note that I've not yet received your leave application form. I would be grateful if you could let me have it as soon as possible.
Regards
Fatema"