The deadline to request a Letter of Invitation is November 1st. Complete one form per attendee, and be sure to include all required information.Letter of Invitation. Complete the invitation letter request form to receive an email with an invitation letter attached (PDF format). To request an invitation letter, please complete the iPRES 2023 Letter of Invitation Request Form. The Bidder shall submit the listed documents in BidBuy under the Attachments tab in the appropriate "Required Attachments" spaces. An invitation letter from you. You must register for the Midwinter Meeting prior to completing the form. Bidder has signed and filled out all Vendor information on the CONTRACT SIGNATURES page. Yes No. B.13 SUBCONTRACTING.