I deal with this issue every day.

As for shipments between the US and Canada here is the answer to your question.

About the NAFTA Certificate of Origin
The NAFTA Certificate of Origin is used by Canada, Mexico, and the United States, including Puerto Rico, to determine if goods imported into their countries receive reduced or eliminated duty as specified by the North American Free Trade Agreement (NAFTA).

For those forms that are completed online, this application is designed for goods whose origin is the U.S. or Puerto Rico only.

The NAFTA Certificate of Origin must be attached to an Invoice if the shipment is valued at greater than:
• $1,000 USD and is being sent to a Mexican destination from Canada or the U.S.
• $1,600 (Canadian dollars) and is being sent to a Canadian destination from Mexico or the U.S.
• $2,500 USD and is being sent to a U.S. destination from Canada or Mexico.


Shipments valued at less than the above amounts do not require a NAFTA Certificate of Origin. Instead, the customer should type the following statement on the shipment’s invoice:

"I hereby certify that the good covered by this shipment qualifies as an originating good for purposes of preferential tariff treatment under the NAFTA."

For purposes of obtaining preferential tariff treatment, this document must be completed legibly and in full by the exporter and be in the possession of the importer at the time the declaration is made. This document may also be completed voluntarily by the producer for use by the exporter. Please print or type.


As for shipments between North America and Europe including the UK - Using FedEx or UPS is possibly faster than the mail service but these companies have recieved the ability to act as their own import brokers and so make money on charging the maximum dutys and taxes.
I have found that the mail service is much cheaper in the long run.

I now include on all my shipping documentation the country of origin and fabric content information. This seems to suffice in most cases.

I do not advocate 'fudging' documentation(I include this legal statement for any and all customs agents which may be lurking here) although I have been known to declare the value of my shipments under the $200.00 personal exemption limit.