What Operating System Can I Use With My Version Of Checkout?
Checkout 5 is compatible with Mac OS X 10.9 (Mavericks) - 10.14 (Mojave)*
*This is the first version of Checkout that is 64-bit, you will notice an immediate all around performance boost especially when using macOS 10.14 Mojave.
Checkout 4 is compatible with Mac OS X 10.6 (Snow Leopard) - 10.13 (High Sierra)
Checkout 3.6 is compatible with Mac OS X 10.6 (Snow Leopard) -10.9 (Mavericks)
Checkout 3.5.7 is compatible with Mac OS X 10.5 (Leopard) -10.8 (Mountain Lion)
If you are considering upgrading your Mac's operating system to something later then 10.9 - you would need to upgrade to Checkout version 4. This is a paid upgrade from Checkout version 3.