When do you use the abbreviation Ms?

Over the years, however, the lack of convention in some style guides has made it difficult to determine which two-word abbreviations should be abbreviated with periods and which should not. The U.S. media tend to abbreviate two-word abbreviations like United States (U.S.), but surprisingly, not personal computer (PC) or television (TV), which is a source of confusion. Many British publications have gradually done away with the use of periods in abbreviations completely.