Offer Document definition clarifies documents inviting public subscription to municipal debt securities and REIT units. The term Offer Document covers any instrument by which an issuer invites public subscription: for municipal debt securities it includes any document, including electronic forms, described or issued as an offer document, prospectus or shelf offer document and advertisements inviting public subscription; for REITs it includes notices, circulars, advertisements and any document inviting offers through a public issue for subscription or purchase of REIT units, including initial and follow-on offer documents and letters of offer in rights issues.