if the customer filed under Chapter 11 of the US Bankruptcy Code, you will want to file a proof of claim. Also immediately get your records together of any payment you received from this customer over the last 90 days prior to the bankruptcy filing. In order to avoid a preference claim from a trustee it in the bankruptcy, you will need to have your record showing that there was either new value or a contemporaneously exchange avail you at the time you were paid. 1 way or another, you will want to hold on to these records until the bankruptcy has been confirmed and the company has emerged. You will want to make sure before getting rid of the records that you have spoken to the trustee and that there is no intention to go after preference claims.