Incorrect Tax when cart has different VAT ratings + a % discount is applied

-- HikaShop version -- : 3.2.0
-- Joomla version -- : 3.8.0
-- PHP version -- : 7.1.10
-- Browser(s) name and version -- : All
-- Error-message(debug-mod must be tuned on) -- : Nil

I have just noticed an issue with the calculation of the taxes in all areas when the following conditions are applied.
Cart has items with 2 levels of tax ie:
20%
0%
and a discount is applied before tax as a % of the non taxable amount

I tried to change the VAT setting on the coupon but this doesn't appear to change the result in the orders showing. The amount of tax that is shown appears to be ignoring that the discount has been applied.

An example of what I am seeing is below, the subtotal is before tax, and includes £60 of 0% VAT items.

Subtotal £ 343.83
Discount -£ 17.19 Water17
Shipping £ 0.00 - Free Shipping
VAT £ 53.33
Total £ 379.97

The forumula to calculate the above appears to be:

Subtotal - Discount - Non Taxable amount + Tax amount = Total + Non Taxable amount = Final Total
343.83 - 17.19 - 60 + 53.33 = 319.968 + 60 = 379.968

Where as it should be:

Subtotal £ 343.83
Discount -£ 17.19 Water17
Shipping £ 0.00 - Free Shipping
VAT £ 53.93
Total £ 383.57

(((Subtotal - Non Taxable amount) - Discount) + Tax Amount) + non taxable amount = total
(((343.83 - 60) - 5% or 14.1915) + 20% or 53.9277) + 60 = 383.5662

I am not sure if this is a views issue or a calculation that's completed in the back-end?

I look forward to your response as I have had to set the shop offline due to these calculation issues.

Regards,
Dave

Having another search and it looks like this issue is mentioned in the following post here www.hikashop.com/forum/taxes/872249-disc...tiple-tax-rates.html

I presume the functionality hasn't been built into Hikashop 3 to overcome this issue... Will this be something added to the todo list?

Regards,
Dave

I have solved this issue by disabling Hikashop coupons/discounts and using AwoCoupons as suggested in the post below which works perfectly.

Regards,

Dave