If APHIS personnel need to be physically present in an exporting country or region to facilitate the exportation of plants for planting and APHIS services are to be funded by the NPPO of the exporting country or a private export group, then the NPPO or the private export group must enter into a trust fund agreement with APHIS that is in effect at the time APHIS' services are needed. Under the agreement, the NPPO of the exporting country or the private export group must pay in advance all estimated costs that APHIS expects to incur in providing inspection services in the exporting country. These costs will include administrative expenses incurred in conducting the services and all salaries (including overtime and the Federal share of employee benefits), travel expenses (including per diem expenses), and other incidental expenses incurred by the inspectors in performing services. The agreement must require the NPPO of the exporting country or region or a private export group to deposit a certified or cashier's check with APHIS for the amount of those costs, as estimated by APHIS. The agreement must further specify that, if the deposit is not sufficient to meet all costs incurred by APHIS, the NPPO of the exporting country or a private export group must deposit with APHIS, before the services will be completed, a certified or cashier's check for the amount of the remaining costs, as determined by APHIS. After a final audit at the conclusion of each shipping season, any overpayment of funds would be returned to the NPPO of the exporting country or region or a private export group, or held on account.