Register before checkout – eShop

not easily – changing the cart page to only be seen when logged in might do it.

Changing the checkout page is NOT an option. I have not tested what happens when that page is only viewable to logged in users. (but will check that out at some point)

You can set the page to private, and the checkout then won’t show unless you are logged in.

But also see:

http://quirm.net/wiki/eshop/additional-plugins-and-code-snippets/mandatory-signup/