Respected Sir/ Madam,
I am _______ (name), studying in __________ (department name) department in ___________ (year/ semester) of your University. My student ID number is __________ (mention student ID number).
I would like to bring into your kind consideration that as per the deadline, I was supposed to submit __________ (assignment name) by __/__/____ (date) but unfortunately, I failed to submit the said assignment by the date assigned. The reason behind the same is _____________ (mention reason for non submission of assignment) and I apologize for the same.
I promise that the assignment will be submitted by ________ (date) without any further delays. I shall be highly obliged for your kind support.
Thanking you,
____________ (Your name),
____________ (contact details)