Yes, with Shopify plus, you can have up to 9 expansion stores (so, 10 stores total) including your main one.
However:
Each store has its own database like products, customers, orders, etc are not automatically shared.
So, customer information is stored separately for each store by default. Meaning is a customer registers in Store A, they won’t automatically exist in Store B.
Now to Question is how to share the customer information between stores. Well! to allow customers to log in with the same credentials across multiple stores, you’ll need to use the single Sign-on (SSO) solution that’s where multipass or third party apps like Xross ID come in.
What is Multipass Login?
Multipass is a build in feature available only to Shopify Plus Merchants.
It allows you to:
Authenticate customer once on your main site (e.g., a central login portal or a custom app).
Then automatically log them into another Shopify store (your expansion store without need to re-enter credentials).
If you don’t have a Centralized authentication system then you can use app like Unity Xross ID.
yes, if you are using the Unity Xross ID (by ChannelUnity), your customers can log in to multiple Shopify stores using the same email and Password, without you needing to build a custom Multipass integration.
Unity Xross ID acts as a Centralized identity system between your stores. Customers only need one account, and the app synchronizes it across all connected stores.
Here is the detailed summary in a easier explanation.
Aspect
Unity Xross ID
Multipass
Single login across stores
Yes
Yes
Requires coding
No
Yes
Automatic customer creation in each store
Yes
Yes (via Multipass token)
Order data shared
No
No
Ideal for merchants who want a quick, no-code setup