Dear

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.