This is the way Honda radio codes work in the US:
The code is provided on a small card. In some cases it is on a sticker inside the glove box
If you cannot find it anywhere, you will need to hold down the 1 & 6 buttons and turn the ignition to on and the radio on, this should display the radio serial number. (Honda newer than 2002) With that, the guys at the parts counter can lookup the code. I don't think there is any way to look it up with the VIN number. If one has the code, you can register at the Honda owners site and keep track of it there.
On the newer Hondas, when it asks for a code you just press and hold the radio power button and the radio checks with the car's computer to make sure the radio is the one associated with it. There is no code