Very Late Reply to Customer

{Date}

To: {Name}
      {Address}
      {City, State, Zip}

Dear {Recipient},

I have been going through old files, and I realized that it has been {length of time} since I first contacted you regarding {reasons for contact}.

I haven't heard from you, and I apologize for taking so long to follow up. I have attached {what you have attached} so that you can see that we can offer you {what you can offer the customer}.

I will be contacting you again on {date}, but if you have any questions or concerns before then, please don't hesitate to give me a call. I look forward to speaking with you.

Thank you,

{Sender}