41 CFR § 301-11.13
How does sharing a room with another person affect my per diem reimbursement?
June 9, 2020
Your reimbursement is limited to one-half of the double occupancy rate if the person sharing the room is another Government employee on official travel. If the person sharing the room is not a Government employee on official travel, your reimbursement is limited to the single occupancy rate.