Dear

Apology to Receiver of NSF Check
When I received your letter of (date) with my check
attached marked "insufficient funds", I called my bank
immediately.

The gentleman I spoke with, (name) , discovered
that the bank had failed to credit my account with a
substantial deposit I had made several days prior.

The bank has assured me that they will be sending you a
formal letter of apology for their error. Attached is my
check in the amount of $ to replace the dishonored
one you have returned.

Thanks & Signature