In lieu of completing and delivering this Letter of Transmittal,. A proposal acceptance letter is a formal written communication one organization sends another to confirm interest in contracting services.Bidder is requested to fill out the Bid Form and attach a completed copy of the specifications (Pages 1. 13) to the Bid Form. 8. Define Letter of Acceptance of Tender. Failure to completely fill in the tender forms e.g. Form of Offer, declaration of interest will result in a tender deemed non-responsive.