When it looks like a late-paying customer may turn into a non-paying customer, you must approach the situation with tact. Start by sending a letter summarizing all the previous contacts you have had and with whom regarding the past- due invoice. Inform the customer that the unpaid invoice will be referred to a debt collection agency after a specific date. Send the letter certified mail with a return receipt so you can prove the letter was received, should you need to take legal action.
If you find that the customer has declared bankruptcy, you should submit a proof of claim and supporting documentation that explains the debt with the bankruptcy court where the bankruptcy was filed. You must also stop sending past-due notices or calling about the debt. While there is no guarantee that your debt will be repaid, your proof of claim will be on record so the court-appointed trustee can determine if and how much you can be paid once the company is reorganized or liquidated.
Lack of communication between customer and supplier is often a root cause of tension surrounding payments. Some customers may be unable to pay in compliance with initial terms, and you need to communicate with your client on this.
Make sure you document everything. Every time you talk to a client on the phone, follow the conversation by sending an email with the details of what you agreed upon. Certify and copy every letter you send in the mail and save email correspondence.