Dear :

We've been very pleased with our business relationship with you over the past years, and we hope to keep you as our valued customer.

I'm concerned, however, by your current account balance, which is days over due. According to our record, you now owe a total of $. Would you please check your accounts and make the payment immediately?

Please call me at [phone number] if you need further information or assistance.

Sincerely yours,

[name]

[title]