A proof of claim is a document filed by a creditor that asserts a right to payment.  In a Chapter 13 case, the creditor must file a proof of claim to receive payment from the Chapter 13 trustee under your plan.  In a Chapter 7 case, creditors may be asked not to file a claim until the Chapter 7 trustee determines whether there are assets for distribution.  Since the claim is filed with the Court, you may not necessarily receive a copy of the claim from the creditor.  Your attorney can assist you in determining whether the claim is valid or should be disputed.  You may use ePOC or Official Form B410 for filing a proof of claim on behalf of a creditor.