If you put the letter K after a number to talk about money, it means “thousands.” 1K stands for $1,000, and 100K means $100,000. Both capital and small Ks are usually accepted and understood.
Always, the letter comes after the number. The dollar sign is sometimes used, but it is not required. Use a decimal point with one number after it when talking about numbers that don’t easily round to a thousand. For instance, $12,555 can also be written as “$12.5k.”
Money is also talked about with the letter M. Both “MM” and “M” mean “million.” So, $30MM is short for “thirty million dollars.” It is fine to use two decimal places when talking about millions of dollars ($30.58MM).