This is a free Productive addon. You have to turn it on to be able to use it.
Go to Settings > Addons and turn on Subsidiaries.
This enables you to have multiple billing addresses which you can use on Invoices and Proposals.
Creating a new subsidiary
Once you have activated Subsidiaries, a new button will be added under Settings > Company info - Create new subsidiary.
Create your new subsidiary and it will appear as displayed below.
Creating a new document type
Now you need to create a new Document type that will be linked to this new Subsidiary.
Go to Settings > Documents and click on Add document type.
Select the subsidiary for which you want to create a new document type and fill out the rest of the details too.
Using your new subsidiary when creating an invoice
From now on you will have to select which subsidiary you want to invoice out of.
The document you've previously created will be added as an option you can select.