[Date]

[Addressee]

Dear [Name]:

Thank you for your check in the amount of $ [dollar amount], 
which was in payment of the discount inadvertently taken in 
paying invoice [#].  We are sorry that there was a 
misunderstanding regarding the period of time allowed in 
which to take advantage of our incentive discount.  We 
appreciate having had the opportunity to clarify our policy 
with you. 

If you have any other questions regarding our credit policy, 
please contact us. We will be happy to provide you with any 
information you require. Thank you very much for your 
recent order. 

Very truly yours,