Celtic, as Di said, duty tax is paid by the receiver of the package, and the sender doesn't need that info at all.

I've shipped international for years and never had a problem. What I've heard from Canadians (and I don't know about other countries) is that the private shipping companies like UPS and FedEx charge their own fees to the receiver, in addition to the duties charged by the individual countries -- which can make the total fees on a package more money than the package itself.
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