Hello, it may depend on how long ago you purchased the license and also, may depend on the current version you have on you Mac. If it is running Catalina and you purchased a license more than 6 months ago, you will be required to upgrade since old licenses will not be compatible with that OS. If you purchase your license recently, you can use the same license. NCH offers a license upgrade discount by entering your current registration code at http://www.nch.com.au/upgrade/