Twilio subaccounts allow you to separate resources, numbers, and settings while sharing a balance with the main account, making it easier to segment usage and manage multiple accounts within a project. Subaccounts provide key benefits such as segmented billing, resource provisioning, and additional control over multiple accounts from the same project. However, before migrating to subaccounts, customers using Twilio's message services must consider the opt-out management issue that affects customer opt-outs when moving phone numbers between accounts. To use subaccounts effectively, developers can create a new subaccount, transfer a phone number to it, set up a messaging service with the phone number, and then send a message through the messaging service using the Messaging Service SID in the request.