Discount amount (based on coupon code) displays misleading in cart (excl./incl. VAT)

[anderspirlo]

Preconditions (*)

1. Tested on Magento ver. 2.4.3-p1.

Steps to reproduce (*)

Tax settings - set Catalog Prices under Calculation settings to excluding tax.
Tax settings - set Apply Discount On Prices under Calculation settings to excluding tax.
Tax settings - set Display Product Prices In Catalog under Price Display Settings to including tax.
Tax settings - set Display Prices under Shopping Cart Display Prices to including tax.
Tax settings - set Display Subtotal under Shopping Cart Display Prices to including tax.
Tax settings - set Display Shipping Amount under Shopping Cart Display Prices to including tax.

I created a Cart price rule with a coupon code, where it gives an discount of 10% without any product conditions.
Go to frontend and add a product to cart. Go to cart page and apply coupon code and look at cart summary.
Product Price: $50
Tax: 10%
Coupon: 10%
Shopping Cart Page display:
Since display settings set to including tax. displayed as $55
Since Apply Discount set to Excluding tax: 50 - (10% of 50) = 50 - 5 = 45
Since Apply tax set to After discount : 45 + (10% of 45) = 45 + 4.5 = 49.5
Discount displayed: $5
Tax displayed: 4.5
But since Price display settings set to including tax:
Subtotal = 55 (Including tax)
Discount also should be displayed including tax: 10% of 55 = 5.5
Total = 55 - 5.5. = 49.5

Expected result (*)

1. Discount amount (based on coupon code) displayed incl. VAT, as all other amounts is including VAT.
2. Expected behaviour is, that Discount amount (based on coupon code) is based on Tax Settings for either Display Product Prices In Catalog under Price Display Settings or Display Prices under Shopping Cart Display Prices.

Actual result (*)

1. Discount amount (based on coupon code) displays excl. VAT.
2. Actual VAT calculation is correct, but the amount is misleading.
   

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Please provide Severity assessment for the Issue as Reporter. This information will help during Confirmation and Issue triage processes.

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
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• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.

[m2-assistant]

Hi @anderspirlo. Thank you for your report.
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[anderspirlo]

@magento give me 2.4-develop instance

[magento-deployment-service]

Hi @anderspirlo. Thank you for your request. I'm working on Magento instance for you.

[magento-deployment-service]

Hi @anderspirlo, unfortunately there is no ability to deploy Magento instance at the moment. Please try again later.

[anderspirlo]

@magento give me 2.4-develop instance

[magento-deployment-service]

Hi @anderspirlo. Thank you for your request. I'm working on Magento instance for you.

[magento-deployment-service]

Hi @anderspirlo, unfortunately there is no ability to deploy Magento instance at the moment. Please try again later.

[m2-assistant]

Hi @engcom-November. Thank you for working on this issue.
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[engcom-November]

Hi @anderspirlo ,
Thank you for reporting and collaboration. Verified the issue on Magento 2.4-develop branch but cannot able to reproduce the issue. Since Price display settings are set to including tax, subtotal is displayed including tax before discount value. Hence breakup details are not matching which is an existing behavior of Magento but not a bug.

Display settings set to excluding tax:

Kindly recheck the issue on Magento 2.4-develop branch and elaborate steps to reproduce if you are still facing issues.
Thank you.

[anderspirlo]

Hi @engcom-November

Thanks for the quick reply. In your first screenshot as far as, I can see, you replicate my settings correctly,
The discount amount displays 5,00 USD (excl. VAT), allthough the correct amount for display should be 5,50 USD incl. VAT.

You write: Hence breakup details are not matching which is an existing behavior of Magento but not a bug.

So this is created by design? I believe it confuses a customers massively, when every amount is including VAT except the discount amount provided in this case.