Is it a bad SEO move to have a your checkout process on a separate domain instead of the main domain for a ecommerce site. There is no real content on the checkout pages and they are completely new pages that are not indexed in the search engines. Do to the backend architecture it is impossibe for us to have them on the same domain.

An example is this page: http://www.printingforless.com/2/Brochure-Printing.html

One option we've discussed to not pass page rank on to the checkout domain by iFraming all of the links to the checkout domain.

We could also move the checkout process to a subdomain instead of a new domain.

Please ignore the concerns with visitors security and conversion rate.  Thanks!