Both address and contact information on a customer, vendor or any party record is stored at the party level. So while the parties Customer and Vendor are company specific the party record is cross company. If you create a customer against the same party in two companies and modify the address of Customer A in company X you will see the changes for Customer B in company Y. This is because when we are modifying a customers address or contact, it is actually modifying the party address and contact. You can test this out without getting into the development environment by creating a customer in one company with an address and contact, note down its party number that was created, then create a customer in another company and use the change party association option to assign the newly created customer the party number of the previously created customer. After this, change the address on any one of the customers and you will see the changes reflect on the other company customer as well. Now generally this is not the case as when you create a customer in a company a new party record gets created against it and within AX you always create a customer or vendor first and not a party itself.
Coming down to the technical’s in play for this. A party record is stored in the DirPartyTable and in order to query its locations(addresses/contact information) you can query the DirPartyLocation table which will give out records that each represent an address and one record that represents all contact information records, to identify these there are NoYes enum fields such as IsPostalAddress. For example if there are 3 addresses on a customer and 5 contact information records, this table will show you 4 records. Each record contains a Location field that represents the RecId of the LogicticsLocation table, this table contains links to the address and contact information records. Addresses are saved in LogisticsPostalAddress table and contact information is stored in LogisticsElectronicAddress table, each table has as relationship with the LogisticsLocation table as shown below.
Contains 4 records, 3 for addresses and one for contacts:
These records can be used to query the address in LogisticsPostalAddress table below, wrt to the following relationship:
Hopefully this gives you an idea of the crud operations of an address and contact information in AX. This applies to both AX 2012 and D365.