The vegascreativesoftware.com website sells only the latest versions. You need to find a reliable established third-party supplier. Beware of unauthorized cracked/pirated copies. Unfortunately most offers online may be such copies.
I WOULD'NT BOTHER .I BOUGHT BOXED VERSION IN 2020 AS A PACKAGE DEAL WITH SOUND FORGE (WHICH IS NOW UNISTALLED BECAUSE OF RENDERING PROBLEMS) AND VEGAS18 PRO WONT RENDER AND NOW ,WONT EVEN OPEN..SAYING "THIS IS NOT A LICENSED PRODUCT" THEY HAVE DONE THIS! THEY ARE NOT ANSWERING REQUESTS.......AND NO, I DONT WANT TO UPGRADE. IVE SPENT HUNDREDS OF £s ON BORIS FX WHICH ARE NOW USELESS......RIP OFF THEFT AND LIES. BUT WHAT DO YOU EXPECT FROM PROFIT BASED COMPANIES.
BTW, if you've already got Vegas Pro 18, you would have had to have registered it in 2020 with MAGIX in order to use it - even with a disk version. In that case, go to My Products in your MAGIX My Account and download Vegas Pro 18 from there - it will be the last build of Vegas Pro 18 which could well be a much later build than the version you have installed from a disk.