As a factoring company, Evergreen must send a Notice of Assignment letter to the account debtors associated with factored invoices. The letter indicates a financial relationship between Evergreen and the sub-contractor; the sub-contractor has assigned all of their accounts and contracts receivable to Evergreen and that all payments owing to the sub-contractor must be sent to Evergreen. Options given for mailing address and electronic payment to Evergreen. This notice is on Evergreen's letterhead and is signed by an officer of Evergreen and our client (the sub). In other industries outside of construction, we normally send this notice through registered email which provides a proof of delivery receipt. Can our document be included with the PN and if so, is there proof of receipt available?