Coupon final charge not correct

-- url of the page with the problem -- : shop.conformance.co.uk
-- HikaShop version -- : 4.2.2
-- Joomla version -- : 3.9.14
-- PHP version -- : 7.3.13
-- Browser(s) name and version -- : Safari

Hi,

I am contacting you on behalf of my client.

They have some products that use the coupon facility, where 10% is deducted.

What they have found is that 10% is being deducted from the original price and the VAT worked out is based on the new price, but the final total is derived from the original VAT cost and not the deducted cost. Here's the calculation (I have also screenshot it as well as setttings in backend).

Cost of product = £35
10% deduction = £3.50
£35 - £3.50 = £31.50
20% VAT on reduced price = £6.30 (this is shown in checkout)
Final charge should be = £37.80
Customer charge = £38.50

We think this is because the VAT on the original £35 is £7
So the £38.50 is calculated by:
£35 - £3.50 + £7.00 = £38.50

They have had this problem for awhile, just not got round to sorting it.

Can you advise on what the issue is.

Any help greatly appreciated.

Thanks

Duncan

Thanks Nicolas,

"Automatic Taxes" wasn't turned on, Configuration was set to "Apply after taxes".

I will give it a test.

Thanks as always for great support.