When included in a business account, each user gets particular sharing permissions (settings). The basic sharing settings come from the Account section of your business account. Those are the so called Admin Share Settings. They define if the account users can Accept External Shares, perform External Sharing and Company Sharing. Regardless of the way those are set, the account owner and the user who holds Account Management permissions can further modify the sharing rights of each user individually by clicking on it and changing their own sharing settings. To do so, open the Users section of your account and locate a user. Click on it and a User Management screen will open. In the User Share Settings section you are given three lists of settings you can modify, so that it suits your needs.