In T 791/06 the intervention of appellant III was considered by the board to be an admissible intervention in opposition appeal proceedings, and so only the required opposition fee needed to be paid, as established by G 3/04. Hence there was no legal basis for retaining the appeal fee, which in any case had been paid as a precaution. The board concluded that the appeal fee paid by the intervener should be reimbursed.

The grounds for reimbursement listed in R. 103(1) EPC aside, fees may also be refunded if there was no legal ground for their payment, e.g. in the event of payment by mistake or overpayment, see Art. 12 RFees e contrario (T 1284/09).