Yes, your Swiss purchase will be, indeed already is, liable for French VAT (18%), provided you are not a company. This is the point of declaring at the border. This way, one can shop in one country, but pay the tax in the resident country.

Now, I'm not a tax expert, but the rules seem pretty simple. Purchases from the US may even add a toll surcharge in the customs.

Whether or not it's worth doing, depends on how much your peace of mind is worth to you.

If I'm wrong, and I could be, then please correct.

The border crossing under the landing strip at the airport is nearly always manned.

There is a customs office at the Bardonnex border.

hello why would you like to detax the computer? by the way the frenc tva is 19.6%

Depends on whether apple.ch participates in the tax free shopping programme. As a frontalier (I presume you are working in GE), I doubt you qualify as a foreign visitor.

Foreign visitors spending more than CHF400 on goods from shops displaying the Tax-free Shopping sign are entitled to claim the VAT back. Make sure you remember to collect an appropriate form from the shop when you make your purchases. Currently VAT added on goods in Switzerland is 7.6%.

To reclaim tax you will need to obtain a VAT refund request form when you make a purchase, which will state the amount of refund due. These documents are then stamped by customs officials as you leave the country and mailed back to the store.

Alternatively you can purchase goods directly from shops participating in Tax-free Shopping (look out for the Tax-free Shopping logo displayed in the window) programme. Simply show your passport when you make a purchase and you will be given a Tax-free Shopping Cheque showing the refund you are owed. As you leave the country, you will need to show the purchases to the appropriate customs official who will stamp your cheques. You can then claim your refund from the Tax-free Shopping desk or have it sent to you.

Incidentally, If during your daily border crossing with your Mac from Geneva into France, you are stopped and checked by the French customs, you will need to show proof that French taxes has been paid for your Mac. Otherwise, you will have to pay the outstanding taxes plus a fine. Of course, this seldom happens but ....