Origin determination for fungible materials permits authorised accounting segregation ensuring parity with physical segregation. Origin determination for products made with both originating and non originating fungible materials may use any inventory management method applicable in the producing Signatory Party; where physical separation is impracticable customs may authorise an accounting segregation method. That method must ensure the number of products treated as originating equals those that physical segregation would have produced, be recorded under the country's general accounting principles, and is subject to conditions, monitoring, and withdrawal for misuse. Beneficiaries may issue or seek proofs of origin for quantities regarded as originating and must provide management statements on request.