The Twilio Phone Number Provisioning API has undergone an important change effective September 10, 2019, due to increased regulatory compliance requirements for phone numbers worldwide. As part of this update, address requirements are now enforced via the API, and users must provide a valid address for newly provisioned regulated phone numbers, with error code 21631 being returned if no address is included. This change only affects phone numbers outside the US and Canada that fail to send an address in their API calls, and existing phone numbers in accounts should have been brought into compliance prior to this update. Regulatory requirements are increasing globally due to fraud, misuse, abuse, and national security concerns, with Twilio working to enable new number types and advocate for smart changes in requirements while preserving value for users. Customers can find more information on regulatory compliance, address requirements, and the change's impact on their accounts through various resources available on the Twilio website.