Cart Price rule discounts incorrect value when shipping is included and an item in the cart is non-taxable

[techsteamdesk]

Preconditions and environment

1. Magento Open Source 2.4.6-p8 without sample data is installed.
2. No custom modules or theme customisation
3. Default Luma theme
4. Set up tax rules and tax rates and zones with a tax rate of 20% for all UK Addresses.
5. Set up the sales > tax configuration as per the attached screenshot. Note that there are no warnings of tax rounding errors.
6. Create a some new products. Create two simple products one that is taxable and one that is not. Create a configurable product with taxable and non-taxable child products. Add all the products to a test category.
7. Set up and enable the flat rate shipping method for £4.80.
8. Create a Cart Price rule that applies a fixed value to the whole cart up to £60 and has the ‘Apply to Shipping Amount’ setting set to yes. See attached screenshot for details.

Steps to reproduce

1. Navigate to storefront as a guest.
2. Open Test Category.
3. Click "Add to Cart" on a Product that is not taxable.
4. Open mini shopping cart and click "View and edit cart".
5. Change the quantity in cart so that it exceeds the £60 coupon discount.
6. Apply the previously configured coupon code.

Expected result

Order is discounted by £60

Actual result

Order is discounted by a different amount.

Additional information

If you change the product in the cart to one that is taxable with otherwise identical conditions the Order is correctly discounted by £60:

However any combination of products in the cart that include a tax free product causes the discount to be incorrect:

Release note

No response

Triage and priority

• 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.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• 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 @techsteamdesk. Thank you for your report.
To speed up processing of this issue, make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce.

• For more details, review the Magento Contributor Assistant documentation.
• Add a comment to assign the issue: @magento I am working on this
• To learn more about issue processing workflow, refer to the Code Contributions.

---

Join Magento Community Engineering Slack and ask your questions in #github channel.
⚠️ According to the Magento Contribution requirements, all issues must go through the Community Contributions Triage process. Community Contributions Triage is a public meeting.
🕙 You can find the schedule on the Magento Community Calendar page.
📞 The triage of issues happens in the queue order. If you want to speed up the delivery of your contribution, join the Community Contributions Triage session to discuss the appropriate ticket.

[m2-assistant]

Hi @engcom-Bravo. Thank you for working on this issue.
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: 👇

• 1. Verify that issue has all the required information. (Preconditions, Steps to reproduce, Expected result, Actual result).
• 2. Verify that issue has a meaningful description and provides enough information to reproduce the issue.
• 3. Add Area: XXXXX label to the ticket, indicating the functional areas it may be related to.
• 4. Verify that the issue is reproducible on 2.4-develop branch
  Details

  - If the issue is reproducible on 2.4-develop branch, please, add the label Reproduced on 2.4.x.
  - If the issue is not reproducible, add your comment that issue is not reproducible and close the issue and stop verification process here!
• 5. Add label Issue: Confirmed once verification is complete.
• 6. Make sure that automatic system confirms that report has been added to the backlog.

[m2-assistant]

Hi @engcom-Delta. Thank you for working on this issue.
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: 👇

• 1. Verify that issue has all the required information. (Preconditions, Steps to reproduce, Expected result, Actual result).
• 2. Verify that issue has a meaningful description and provides enough information to reproduce the issue.
• 3. Add Area: XXXXX label to the ticket, indicating the functional areas it may be related to.
• 4. Verify that the issue is reproducible on 2.4-develop branch
  Details

  - If the issue is reproducible on 2.4-develop branch, please, add the label Reproduced on 2.4.x.
  - If the issue is not reproducible, add your comment that issue is not reproducible and close the issue and stop verification process here!
• 5. Add label Issue: Confirmed once verification is complete.
• 6. Make sure that automatic system confirms that report has been added to the backlog.

[engcom-Delta]

Hi @techsteamdesk ,

Thanks for your reporting and collaboration.
We have re-verified the issue in latest 2.4-develop instance and the issue is reproducible.
Kindly refer the screenshots.

Steps to reproduce :

1. Navigate to storefront as a guest.
2. Open Test Category.
3. Click "Add to Cart" on a Product that is not taxable.
4. Open mini shopping cart and click "View and edit cart".
5. Change the quantity in cart so that it exceeds the £60 coupon discount.
6. Apply the previously configured coupon code.

Observe Cart Price rule discounts incorrect value when shipping is included and an item in the cart is non-taxable.

Thanks.

[github-jira-sync-bot]

✅ Jira issue https://jira.corp.adobe.com/browse/AC-13715 is successfully created for this GitHub issue.

[m2-assistant]

✅ Confirmed by @engcom-Delta. Thank you for verifying the issue.
Issue Available: @engcom-Delta, You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself.