Handle the prices-include-tax and Intra-Community-Supply scenario

If a price is entered with tax (let's say 12eur, assuming a 20% local rate), and Intra-Community Supply (B2B VAT) imposes a 0% rate, the expected behavior is for the price to be reduced.

I'm not sure if that must be true, or should be decided by the shop owner.

Here's why:
When selling products to foreign countries and prices are entered vat-inclusive, you have a similar situation for the different VAT's and you want the total to stay the same, even if the vat rate changes! Otherwise you couldn't show the gross price without knowing the client's details (shipping location & vat id for example!)

So one could argue that it's luck or misfortune for the shop owner, because in each of this cases, the margin is different by design! Is there any law enforcement to reduce the gross amount for intra-community supply?

I believe it’s important to clarify a key distinction between sites displaying tax-inclusive (TTC) prices and those displaying tax-exclusive (HT) prices.

1) For sites displaying tax-inclusive (TTC) prices:
The gross price (TTC) is entered including the local VAT rate (ex: 20% in France). When an intra-community B2B customer provides a valid VAT number, the VAT is simply removed (TTC price - local VAT), leaving the net price (HT). In this case, the shop owner’s margin is not impacted, as the net price (HT) remains constant.
However, for a B2C customer from another country (ex Belgium with 21% VAT), the gross price (TTC) must remain fixed, but the net price (HT) may vary depending on the VAT rate applied. This can slightly affect the margin, but this is required by law for B2C transactions to comply with EU Directive 2006/112/EC.

2) For sites displaying tax-exclusive (HT) prices:
The net price (HT) remains constant, and VAT is dynamically added based on the client’s location and VAT status. In this scenario, the shop owner’s margin is stable, as it is not affected by VAT rates.

This patch correctly adjusts the expected behavior by removing VAT for intra-community B2B sales with a valid VAT number, ensuring compliance with EU Directive. For B2C international sales, the margin variation is a consequence of the legal requirement to maintain a constant gross price (TTC).

I hope this explanation clarifies the distinction and why this behavior is necessary.