Cover letters are not officially part of a submission, but they represent another opportunity to reinforce your messages.
If the cover letter is likely only to be read by the person who accepts delivery, use it to list the contents of the submission and to confirm compliance.
If the cover letter is likely to be read by an influencer or decision-maker:
• Use the cover letter to cite your key discriminator.
• Have the letter signed by the highest ranking person in your organisation that the customer knows.
• Include two or three powerful reasons to select your offer
More information on this subject is in the Shipley Proposal Guide – see COVER LETTERS.