Dear …

RE: Terms of Payment

A review of your account with __(name of Company)__ has revealed that over the past __(# months/weeks/etc.)__, __(Name of Organization)__ has maintained a very poor payment history with our company. Consistently, this account is in an overdue status. Please accept this as your last written notification that this situation is not acceptable and will no longer be tolerated.

Effective immediately, all invoices issued to your organization by __(Name of Company)__, must be paid __(promptly/within the terms of agreement/within 30 days/etc.)__. Failure to do so will result in immediate commencement of collection and legal action, without further notice to you. It is not our wish to affect the credit rating of __(Name of Organization)__, nor to proceed with legal action and have liens placed on your property and such, but make no mistake, we are now prepared to do so if your account is not immediately brought up to date.

Please be fully aware that if this situation is not immediately rectified and if your account with __(Name of Company)__ slips into an overdue status again in the future, our business relationship will be immediately terminated. We hope that you will see the importance in remitting all monies owed to us in a timely manner from now on. Thank you for your acute attention to this matter.

Yours truly,