Magento applies tax on product prices that already including tax

Question

I've added products prices with tax included (in the field Price [EUR] [ Including Tax]) Now when I put a product in the cart, Magento applies the tax to price that already including the tax!

Example: if the product has "Price [EUR] [ Including Tax]"=100€ in the cart I have:

Product price € 100

Sub total € 100

Taxes € 20

Totale €120 (but the correct price including taxes is 100€!)

instead I want this:

Product price € 100

Sub totale € 80

Taxes € 20

Total €100

I'v tried all the settings and I'm going mad! is there a solution?

Answer 1

I will repost idophir's comment, that fixed my issue that led me to this question. I wasted hours looking at tax settings and tax rules, to finally find my culprit in shipping origin settings:

Check out the link below. It says that the shipping origin country (System > Configuration > Sales > Shipping Settings > Origin) affects the the way the price is displayed in the cart. Strange.. http://www.magentocommerce.com/boards/viewthread/78069/