I have a project in which we were able to provide invoices for 92% of all wood based product in the project. The one product we were not able to get an invoice for (accounting for the remaining 8%) is an acoustical wall panel that is comprised of 20% wood fiber. This is a non-FSC product.

Our reviewer has mandated that we provide an invoice for the wall panel. Unfortunately, we are in a position where the installing subcontractor and the vendor are both no longer in business. There is no opportunity for us to acquire the invoice.

Given that the acoustical wall panels do not contribute any FSC content, would a signed letter from the general contractor attesting to the material cost be sufficient in this case?