Post by ATVDevelopments » Thu Apr 22, 2021 7:48 pm

When a coupon is applied it is not producing the correct outcome.
I created a coupon with 15% discount and it in fact produced a final figure which resulted in a 2.5% discount (1/6 of 15%)
To test this again I created another coupon of 90% and applied this to a product and the checkout total was correct for 15% but the VAT figure is way out.
In summary:
Product net value £851.00
Including VAT £1021.20
The 15% discount code produced a total invoice value of £995.62
I created the -90% test code
The 90% discount code produced a total invoice value of £868.02 (which is 15%)
The VAT showed as £17.02, which is just the difference between the non-discounted net price and the gross.

I have no idea what is going on here. Can anyone suggest a solution?
Thanks in advance



x6.JPG (18.71 KiB) Viewed 202 times

I don't have many custom extensions installed, just the Square payment (
My site is
The opencart version is


Thu Oct 22, 2020 4:10 am
Location - UK

Post by paulfeakins » Fri Apr 23, 2021 7:39 pm

ATVDevelopments wrote:
Thu Apr 22, 2021 7:48 pm
I don't have many custom extensions installed
Any discount related ones?

For quick, professional OpenCart support please email

User avatar
Guru Member


Mon Aug 22, 2011 11:01 pm
Location - Reigate, Surrey, United Kingdom

Post by Johnathan » Fri Apr 23, 2021 10:12 pm

I think your Order Totals are in the wrong order. You must always have "Sub-Total" first and "Total" last in OpenCart, otherwise you're likely to have calculation issues. Try changing the Sort Order of them in Extensions > Order Totals so that they are in this order:


That will hopefully fix it for you, but if not, post another screenshot from Step 6 of checkout with the incorrect calculation, and we'll see if there's any other clues.

Image Image Image Image

User avatar
Global Moderator


Fri Dec 18, 2009 3:08 am

Who is online

Users browsing this forum: No registered users and 35 guests