[4.x]: Commerce discounts applying before tax?

[robzor]

What happened?

Description

Hi there,

We have a Commerce store with products that either have 20% tax or 0% tax so we have a VAT tax rule of 20%:

If we create a discount, for example, 30% off:

If a customer adds products to their cart (note: the majority of our products do have VAT tax applied), then the discount gets applied to the cart price before tax is added. So with a £50 (inc. VAT) product, a customer who applies the 30% off voucher expects to get £15 off, but instead only gets £13 off. Here is an example of the cart with both VAT and non-VAT products in:

Is it possible that we can set it that Commerce discounts apply after tax?

All prices on the site are displayed including tax (this is the norm in the UK) so the client (and customers) are struggling to understand why the discount is not 'what is expected'.

Steps to reproduce

1. Create tax category of 20%
2. Create discount of 30% off (Per Item Percentage Off)
3. Add items to basket
4. Add discount code

Expected behavior

Discount applies after VAT is added

Actual behavior

Discount applies before VAT is added

Craft CMS version

4.3.10

Craft Commerce version

Pro 4.2.5.1

PHP version

No response

Operating system and version

No response

Database type and version

No response

Image driver and version

No response

Installed plugins and versions

[cherrykoda]

Surprised there isn't an available option in the discount setup... seems like Line Item + Line Item Tax should be an option here.

[pdaleramirez]

@robzor You can re-order the adjustment by doing this.
E.g.

        Event::on(
            OrderAdjustments::class,
            OrderAdjustments::EVENT_REGISTER_ORDER_ADJUSTERS,
            function (RegisterComponentTypesEvent $event) {

                $event->types = [Tax::class, Discount::class, Shipping::class];
            }
        );

The screen you’ve shown seems to be not an included tax setup.

Luke: Please note we do not recommend doing this as we expect tax to run last.

[robzor]

@pdaleramirez Hi there, thanks for getting back to me.

I'm not sure what you mean by "not an included tax setup".

Where would I put the code you've provided?

Thanks!

[robzor]

Hi @pdaleramirez , I've worked out how to make a custom module and used your code snippet but while this has reordered the tax to come before the discount, the discount total is still being calculated from the original price. 

This is actually worse than before, as it is saying "you get 30 off the non-VAT price, but you still have to pay the original VAT amount":

What we need is for the discount amount to be calculated including tax. So in this screenshot, on the second item, the discount total would be £43.20 (30% off (£120 + £24)).

Is there a way to tell the discount adjuster to use that line item + tax value?

[lukeholder]

@robzor I am seeing the issue with the opening post.

30% off 120 is 84, and 20% tax on 84 is 16.80?

[lukeholder]

If you say:

What we need is for the discount amount to be calculated including tax.

Then you need the tax amount included in the price you enter for the product:

[robzor]

Hi @lukeholder thanks for getting back to me.

Unfortunately we have over 4000 variants on the site including bulk discounted prices so there is no easy way to change them all at this point.

It's a shame that while the tax adjuster takes the running subtotal, e.g. after discount it applies to the new subtotal but the discount adjuster doesnt.

As shown above you can see that when I reordered the adjusters as per @pdaleramirez 's code snippet, the discount adjuster still used the original item price.

I'm really not sure how to proceed here, have you got any other suggestions?

[robzor]

To add to this, I think what would be the ideal scenario is if the 'Taxable Subject' rule in the Tax rule setup has another option, "Line Item Price" as well as "Line Item Price (Minus Discounts)".

Can you think of a way I could 'hack' this in?