Tax calculation Wrong with coupon discount

[info@.....com]

We have a problem with the tax not beeing calculated correctly if a discount coupon is beeing used (either in percentage or amount). We show the prices in the cart including Tax, Shipment cost is inculding tax as well. We have a taxrate of 21%.

Poduct amount Price Subtotal
Shoes 1 EUR 39,95 EUR 39,95
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Subtotal EUR 39.95
Couponcode test 10% EUR -4,00
Shipment costs EUR 5,95

Total EUR 41,90
Total tax EUR 6,97

The total tax should be EUR 7,27. I tried several settings in Onepage checkout (although the default is salesPriceCoupon). We have a tax rule of VAT tax + 21% in Virtuemart applied to all shoppergroups and all products.
I can't seem to figure out what causes the Tax calculation to be incorrect. Without coupon codes, the calculation works as aspected.
How can we fix this problem?

[admin]

hello, opc itself does not do any sort of calculation, but it relies on virtuemart to do the calculation.

the most common issue with taxes is caused when having a tax rates on shippnig or payment plugins. i suggest that you put "no tax/rule" per each of your shipping and payment plugins and see if the tax gets calculated properly when the coupon is used.

if this didn't help, i suggest that you try this with opc disabled and if you get the same problem, you either may want to try various versions of "calculationh.php" file from vm2.0.20 to 2.6.x or ask VM core team to get this solved finanally.

your tax mode also plays a huge role in this. if you are based in EU, you should use "vat rules".

let us know if this helped:
- the no tax on shipping/payment when coupon is used

best regards, stan

[info@.....com]

Ok, I tried it with tax disabled on Shipment and payment method, the same problem appears.

I also disabled OPC completely, and the same error is visible. So, you are right, nothing to do with OPC, only with VM.

I will try different versions of calculationh.php and get back with the results...

[info@.....com]

Different versions dont fix te problem. I should probaly post this problem in the VM forums...

[admin]

hello, i would suggest to use version 2.0.18a of the calculationh.php. We can have a look on the details of your issues next week. If you are using awo coupons, pls try to create the same plugin in core vm coupons and see if the calculation is still wrong (when awo completely disabled).

best regards, stan