Postal Code

Is the distance calculation based on the postal code? Does that mean we need to enter the postal code of the area we picked up the bill or can we use our home postal code? Any thoughts?

your home postal code is fine.

Yes, the distances are calculated by the postal codes.

You can enter either where you are entering the bill (home, work, or school) or where you acquired the bill.

I usually try to enter the postal code of where I received the bill. But if I can't remember or find the postal code, then I enter my home postal code.

I usually enter my home postal code.. as that is where i enter the bill.
If I am travelling. I try to find the postal code of where I got the bill or hotel I stayed at.
In the case when I am travelling I usually write down the serial numbers & where I got it.. to enter when I get home.