What is the meaning of Official Statement (OS) or Offering Circular (OC)?

Official Statement (OS) or Offering Circular (OC) is a document (prospectus) circulated for an issuer prior to a bond sale with salient facts regarding the proposed financing. There are two OSs, the first known as the preliminary, or "red herring" - so named not because it smells but because some of the type on its cover is printed in red - and it is supposed to be available to the investor before the sale. The final OS must be sent to the purchaser before delivery of the bonds.