When a company sells under several brands, someone eventually asks the obvious question: why can't customers put products from every brand into one cart and check out once?

It sounds like a small improvement to the shopping experience, but it isn’t a small feature. A shared cart between brands, on Drupal Commerce at least, is relatively easy, assuming each brand runs from the same Drupal installation. 

But that’s only half of the story. What happens after the order is placed? The hard part of a shared cart experience is everything after checkout, especially fulfillment.

How the cart works by default

In a multi-brand Drupal Commerce setup, each brand gets its own store entity. A store holds a brand's commerce settings:

• Which merchant account takes the payment
• Which prices and promotions apply
• Which payment methods are available

Once something like Commerce Store Domain is installed and configured, a shopper's cart belongs to the store of the brand they're browsing.