Respected Sir/Madam,
I am _______ (name) and I am working as ________ (designation) in your organization for last ________ (duration). My employee ID number is _______ (mention employee ID).
This is to most humbly request you to sanction leave for one day i.e. on __/__/_____ (date) as I have to attend a family function on the said date.
In my absence, __________ (name) will be handling my work and I shall be highly obliged for your kind consideration of my leave request.
Thanking you,
___________ (Name),
___________ (Designation),
___________ (Employee ID)