If you were late in submitting your assignment, here is a sample template you can use to write an apology letter or late submission of an assignment .
Subject: Apology for Late Submission of Assignment
Sir/Ma’am, please accept my sincere apologies for the late submission of the assignment that had been handed out on [Date]. It was supposed to be submitted on [Date]. However, I had unexpectedly faced some unavoidable circumstances [Explain the Reason]. I had tried my best to submit the assignment on time but failed to do so.
I promise never to repeat this in the future. I hope you can forgive this instance of an unintentional mistake and accept my assignment. I will be grateful for your help and consideration.