Waiving travel expenses payments by third parties
In general you can waive your entitlement to reimbursement for travel expenses on business trips. However, for insurance reasons, make sure that you make a business trip application and explain on this application that you waive claims to reimbursement for travel expenses.
Payments received by business travellers by third parties on account of their business trip are to be credited to the travel expense allowance. These include such things as subsidies granted from another office to execute the business trip, but also benefits which have been granted on account of previous business trips (such as frequent flyer miles).