If the beneficial owner decides to be subject to the 35% "retention" tax under the EU-CH agreement, upon filing the Greek tax return, that tax is fully creditable, with possible subsequent reimbursement by Greece under Article 9(1) of the EU-CH agreement: "Where this amount exceeds the amount of tax due on the total amount of interest subject to retention in accordance with its national law, the Member State of residence for tax purposes shall repay the excess amount of tax withheld to the beneficial owner.". In the example, the "retention" tax under the EU-CH agreement is 500*0.35=175. 75% of that EUR 175 (175*0.75=131.25) would be transferred "anonymously" to Greece. Upon filing his tax return, the Greek beneficial owner is entitled to full credit, not only for the amount paid to Greece (EUR 131.25), but for the total "retention" tax levied under the EU-CH agreement (EUR 175). Therefore, if the Greek tax liability would be 500*0.10=50 and the credit would be EUR 175, the credit would cover 100% of the Greek tax liability and would exceed it by 50-175=-125. That excess credit (EUR 125) must be refunded to the beneficial owner by Greece.