I've had to pay duty on items from the US - the worst was for a Christmas gift sent out to all employees from the US company I worked for! It's the declared value which causes the issue I believe.
I'm currently waiting for a parcel collection today to go to our son in NZ - it's a snare drum for his kit so quite a large box. I've had to fill in a pro-forma invoice with the value which we put as negligible as its an uninsurable item so he won't pay duty on it anyway. They've never had to pay anything at their end when I've sent things before.
Well, well. Is it ‘global warming’ or ‘cloud seeding’?