Connecting business trips with personal trips
(§ 13 Bundesreisekostenrecht - German regulations for travel expenses)
If business trips are connected to personal trips, the travel expense reimbursement is rated as if the business trip alone had been undertaken. The personal trip is not permitted to affect the amount of travel costs to be reimbursed. Regardless of when the business portion takes place (before, during or after a personal trip), the travel expense reimbursement is measured as if the business travellers had travelled to the business location immediately before the business meeting and returned home immediately afterwards.
If a holiday lasts more than 5 working days, the trip is classified as a mostly personal matter. In this case, the only items which will be reimbursed are the direct additional travel expenses caused by the business meeting, and the daily and overnight allowances for the duration of the business meeting. It is irrelevant whether the business trip or the holiday was planned first.