USCG boat documentation number Each documented vessel receives a Certificate of Documentation (COD) that includes this number. The number must be permanently marked on an interior structural part of the hull in block-style characters at least three inches high. The prefix “NO.” must appear before the number to clearly distinguish it from other identifiers. Once assigned, the number remains with the vessel throughout its lifetime, even if ownership changes. Visit : https://usvesselregistrar.us/uscg-documentation-number/