FYI TO ALL
If your laptop computer was made in Japan—for instance—you might have to pay duty on it each time you bring it back into the United States, unless you could prove that you owned it before you left on your trip. Documents that fully describe the item—such as sales receipts, insurance policies, or jeweler's appraisals—are acceptable forms of proof.
To make things easier, you can register certain items with CBP before you depart— including watches, cameras, laptop computers, firearms, and CD players—as long as they have serial numbers or other unique, permanent markings. Take the items to the nearest CBP office and request a Certificate of Registration for Personal Effects Taken Abroad (CBP Form 4457). It shows that you had the items with you before leaving the United States and all items listed on it will be allowed duty-free entry. CBP officers must see the item you are registering in order to certify the certificate of registration.
You can also register items with CBP at the international airport from which you’re departing. Keep the certificate for future trips.
This was taken directly from the US Customs and Border Protection website:
http://www.cbp.gov/xp/cgov/travel/vacation/kbyg/register_items.xml
I plan on going to the airport a bit earlier than I need to try this out. I'm a little worried because I am bringing in a netbook, a DSLR two lenses and a flash, as well as a macbook. The macbook is only a couple of days old and I will be leaving in two weeks, so I really don't want to get hassled for it at the airport. I had no idea you could do this. Has anybody done this before? I am assuming this applies for Argentina as well as it will prove ownership of my electronics. I also saw somethign similar on the Frommer's website:
In Argentina, this is rarely an issue unless you have a lot of electronics. To avoid having to pay duty on foreign-made personal items you owned before you left on your trip, bring along a bill of sale, insurance policy, jeweler's appraisal, or receipts of purchase. Or you can register items that can be readily identified by a permanently affixed serial number or marking -- think laptop computers, cameras, and CD players -- with Customs before you leave. Take the items to the nearest Customs office or register them with Customs at the airport from which you're departing. You'll receive, at no cost, a Certificate of Registration, which allows duty-free entry for the life of the item....................
I guess I could also just bring along receipts for my camera and laptop too. Hmm.