In a business report, a minimum of single space should be used between each line. However, Purdue University’s Online Writing Lab recommends using white space to enhance information. Dense blocks of text make it more difficult for a reader to process the information.
While there is no definitive answer, the key is to ensure that the text is accessible to the reader. If the report has large blocks of text, the spacing between the lines should be adjusted to at least 1.15. If blocks of text with white space, charts or graphics are used, then it is permissible to use single spacing between lines.