[Date]

[Addressee]

Dear [Name]:

When I received your letter of [date] with my check
attached marked "insufficient funds", I [list actions
you made in researching the matter].

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.

Yours very truly,