In connection with VAT refunds, as Peter Greenberg discusses June 15, there is a point that might be helpful to people who do not have time to wait for the customs stamp when they are leaving the country, or are leaving from a port where there is no customs official. The VAT forms can be notarized in the U.S.A. and mailed from here to the store responsible for the refund.
Another possibility is, if the refund is coming from one Common Market country, to have the form stamped on exit from another Common Market country. This spring, for example, I left England from Liverpool on the Dublin ferry. There was no English Customs at Liverpool, but I was able to get the forms stamped at Shannon and mailed them from there.
Many stores will take care of VAT refunds by crediting your charge card, which nicely sidesteps the problem of currency conversion.