41 C.F.R. § 301-11.14
Agency reimbursement for return home or to the official station during TDY
The agency may authorize per diem or actual expense and round-trip transportation expenses for periodic return travel to the employee's home or official station under the following circumstances:
(a) The agency requires the employee to return to their official station to perform official business;
(b) The agency will realize substantial cost savings by the employee's return home; or
(c) Periodic return travel home is justified as part of an extended TDY assignment.