Code of Federal Regulations Title 41. Public Contracts and Property Management § 41.304–3.11 Am I limited to the maximum subsistence allowances (per diem or actual expense) prescribed in applicable travel regulations for travel expenses paid by a non–Federal source?

Generally yes. Subsistence expenses are usually limited to the maximum subsistence allowances (per diem or actual expense) prescribed in chapter 301 of this title for travel in CONUS, by the Secretary of Defense for travel in non-foreign areas and by the Secretary of State for travel in foreign areas. However, acceptance of payment for, and when applicable, reimbursement by an agency to an employee and the accompanying spouse of such employee are not subject to the maximum per diem or actual subsistence expense rates when traveling in CONUS or in non-foreign areas under the following conditions:

Note:  The maximum subsistence allowances established by the Secretary of State for travel to foreign areas may not be exceeded.