Hi Paul,
By default the cart keeps the data (categories, products, etc) seperate by portal which is the desired behavior since in most cases each portal is for a unique company/domain.  Currently, the cart has a share flag for categories and products that allows you to share categories and products across buynow modules within the same portal but the cart doesnt have a setting that allows you to share products across portals.  If you would like a quote to add that feature please send an email to sales@smith-consulting.com.

As an alternate approach you could manage your category and product data in an xls and then use the product import feature in the cart to import your data to each portal.  This would give you the ability to manage all your products from a central location and prevent duplicate data entry.  I know the best solution would be for us to create a "share products across portal" checkbox in the product setup screen but importing gives you an alternative that is available in the cart now.

Thanks,

Kevin