Hello, if I purchase the deluxe software will I also need to purchase the business software in order to file my business taxes (due in March)?

Yes if you need to file a separate business return like a 1065 or 1120.  You need to buy Turbo Tax Business, not to be confused with the personal Home & Business version. TT Business is not available to do online or on a Mac. You can buy the Windows Desktop program here,
https://turbotax.intuit.com/small-business-taxes

You can have both a personal version and the Business program installed at the same time.