Goods total excluding shipping can be 1000 or less. If over 1000 they will charge gst on the goods, PLUS gst on the freight.
The calculator works.
Also, depending upon the item it may not attract duty even though gst kicks in along with other fees.
We're actually in a better position than back in the days of the old $60 kick in so to certain extent the bricks and mortar shops have lost out a bit but will have gained on things like clothing purchases from the big overseas outlets who are mostly now collecting gst on behalf of the govt. Likewise any Amazon purchase now attracts gst.
The issue with having something that converts close to the $1001 is that after you push the buy button an unfavorable exchange rate movement could take you over the threshold. The value of your goods are assessed at the border on arrival, not what your CC may have been billed.
Be careful of the exchange rate in the calculator, it doesn't seem to line up exactly with official exchange rates which are constantly moving.
It's still a good estimator though.
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