Modern business letters typically use one of two styles of punctuation: mixed punctuation and open punctuation. There are three main styles of business letter: Block style, Modified Block Style, Semi-Block Style. 14 Essential Parts of the Letter: Sender’s Address or Headings, Reference Number, Date, Recipient Address/Inside Address, Attention Line, Salutation, Subject Line, Body of the letter, Formal Close, Signature slot/block, Enclosures, Postscripts or P. S., Carbon Copy notation/copy furnished ‘C C’, Reference Initial