20 C.F.R. § 10.506

The employer may monitor the employee's medical progress and duty status by obtaining periodic medical reports. Form CA-17 is usually adequate for this purpose. To aid in returning an injured employee to suitable employment, the employer may also contact the employee's physician in writing concerning the work limitations imposed by the effects of the injury and possible job assignments. (However, the employer shall not contact the physician by telephone or through personal visit.) When such contact is made, the employer shall send a copy of any such correspondence to OWCP and the employee, as well as a copy of the physician's response when received. The employer may also contact the employee at reasonable intervals to request periodic medical reports addressing his or her ability to return to work.