Comma in Numbers (Thousands Separator)

Use a comma in numbers of four or more digits to separate hundreds, thousands, millions, and billions. Do not use commas in numbers that represent house addresses, page numbers, policy numbers, social security numbers, street numbers, telephone numbers, years, or ZIP Codes. Patent and serial numbers from the U.S. Patent Office do retain commas. If a number is verbalized in even hundreds, it may be written without a comma.