An assigned RIN must appear in its entirety on product transfer documents (PTDs) identifying a transfer of ownership of a volume of renewable fuel. Substitute codes are not permitted. See regulation Section 80.1153. (In general PTDs would not include bills-of-lading, which are used for transfers of custody rather than transfers of ownership.)
However, the PTD transferring the RINs can be a separate and parallel PTD from that used to transfer the renewable fuel to which those RINs are assigned. In this case, the PTD transferring the renewable fuel must include the number of gallon-RINs being transferred and a unique reference to the PTD which is transferring the assigned RINs, but need not list the actual RINs. See regulation Section 80.1153(a)(5)(ii). PTDs can be electronic, including computer spreadsheets.
Question and Answer was originally posted at: Questions and Answers on the Renewable Fuel Standard Program (PDF) (55 pp, 221 K, EPA420-F-07-041a, August 2007, About PDF)