_________ (Mention recipient’s details)
Date: __/__/_____ (date)
Subject: Apology for the delay in issuance of invoice
Dear ___________ (mention name of client),
First of all, I would like to apologize for the delay that you have faced in issuance of your invoice ____________ (mention invoice ID) for __________ (order number). Respected, I understand that all this happened was due to negligence and was a reflection of unprofessionalism.
We apologize for the inconvenience that we have caused. We are hereby attaching the invoice along with the letter and we request you to kindly send your acknowledgment. Furthermore, we apologize for the delay and believe that you would give us another chance to serve you better.
__________ (Company Name),
__________ (contact number)