Dynamics 365 for Finance supports using a shared number sequence for customers. This way, customers in one legal entity have the same customer number if they exist in another when created from the All customers list. When creating a Customer from the All customers list page, and entering the name of a Customer that exists in a separate legal entity, the "Existing customer. Copy customer?" toggle box is visible, and can be turned on to copy the Customer and its Customer number from the other legal entity. However, this toggle box is NOT visible when creating from the Global address book Party action pane's Customer button, when the Party in question has a Customer in another legal entity. Compare this to Vendors/Accounts Payable, where the "Existing vendor. Copy vendor?" toggle box available from both the GAB and Vendors list. As a result, the functionality is asymmetrical and will lead to multiple customer numbers pointing to the same Customer.