Can I delete the sent SMS in the background of my mobile phone?

I can't. According to the query of Pacific computer network, it is not supported to delete the SMS sending record actively. According to the service agreement, the business halls of China Unicom, China Mobile and China Telecom will keep the short message sending records of users in the past two months for users to check and reconcile, and the short message records after February will be cleared regularly. As time goes by, the first record will be deleted automatically.