How To Write A Formal Letter In Block Format . Semi block or indented style is similar to a full block style, albeit informal. Let’s see an example of a formal letter of complaint. 2020 Block Letter Format Fillable, Printable PDF & Forms Handypdf from handypdf.com Place your name and address at the top of your letter. Set top and bottom margin to 1″ or 1,5″ if you have less text; Modified block differs from block style in that the date, sign off, and signature lines begin at the centre point of the page line.