Can parallels be upgraded regardless of version number?

I have parallels 9 and want to know if I can upgrade to Parallels 15. I am aware I have to pay the price for the upgrade, but I am just wondering since my parallels key is so old.

 

Hi, yes, now you can upgrade to the Parallels Desktop 15 from any previous Parallels Desktop version. Your Parallels Desktop 9 key will work as an upgrade key.
Please let us know if you have any additional questions.