As a rule, each party to proceedings before the EPO meets the costs he has incurred. This principle notwithstanding, the competent body in the opposition proceedings may for reasons of equity (see D‑IX, 1.4) decide to apportion in some other way the costs arising for the parties in respect of oral proceedings or taking of evidence (see D‑IX, 1) and the costs arising for the EPO in respect of witnesses and experts (see E‑III, 1.10). The competent body may make the taking of evidence conditional upon deposit with the EPO by the party who requested the evidence to be taken of a sum the amount of which is to be fixed by reference to an estimate of the costs. This procedure should be applied where at the request of a party to grant or opposition proceedings evidence is to be taken by hearing witnesses or seeking an expert opinion, unless no costs will arise because the witness or expert has waived his right to indemnification. If the party requesting evidence to be taken does not comply with the requirement of making such a deposit, the evidence need not be taken. In opposition proceedings the party requesting the evidence bears the costs of indemnifying witnesses or experts, unless for reasons of equity in individual cases other arrangements are made for the apportionment of costs under Art. 104(1) in conjunction with Rule 88. Any shortfall between the deposit lodged and the amounts payable by the EPO under Rule 122(4), 2nd sentence, is fixed by the EPO of its own motion. Any unused amount of the deposit lodged is refunded. The Office's EPO’s internal costs arising through oral proceedings or taking of evidence, e.g. any associated staff travel and subsistence costs, are to be met by the EPO itself.