Q. What is the APA format for writing a MEMO?

From Purdue OWL's page on citing a memo:  

"The format of a memo follows the general guidelines of business writing. A memo is usually a page or two long, should be single spaced and left justified. Instead of using indentations to show new paragraphs, skip a line between sentences. Business materials should be concise and easy to read. Therefore it is beneficial to use headings and lists to help the reader pinpoint certain information."