Proof of claim: operational creditors must file Form B and substantiate debt with contracts, invoices, or records. An operational creditor (excluding workmen or employees) must submit proof of claim in Form B to the interim resolution professional, in person, by post or electronically, and may provide supplementary documents before committee constitution. Existence of the debt may be proved by records with an information utility or by other documents, including a supply contract, an invoice, a court or tribunal order on non payment, or financial accounts.