Magento 2.3: Klarna + Coupon Code results in “main.ERROR:Order line totals do not total order_amount”

Question

Klarna Payment method is activated in the checkout. It works fine as long as you don't use a coupon code. If you do, the checkout page breaks with the following error:

main.ERROR:Order line totals do not total order_amount - 530 != 490

Here is what I did already:

• Deactivated ALL third party modules
• Activated Luma Standard Theme
• Deactivated all other payment methods
• Went through the database in the hope to find anything
• Tested different tax and pricing settings
• Updated from 2.3.3 to 2.3.4

Does anybody have an idea what I could have missed? Or what I should test next?

Using Magento 2.3.3 (live) and 2.3.4 (dev). Happens on both instances. Live and Dev are located on different servers.

Answer 1

I was able to solve the issue by setting the "Apply customer Tax" to "Before Discount":

Shop => Configuration => Sales => Tax

Standard Setting is:

Now I receive a Magento Warning in the backend. But at least everything works. Still, I think there is something wrong with Klarna Payment.

Answer 2

According to https://www.klarna.com/assets/sites/15/2020/03/04081615/user_guides.pdf page 15

This is proper M2 tax configuration to work with Klarna

General Tax Calculation

• “Tax Calculation Based On” should be set to “Shipping Address”
• “Apply Customer Tax” must be set to “After Discount”

Tax Calculation for non-US countries

• “Tax Calculation Method Based On” should be set to “Row Total”
• “Catalog Prices” must be set to “Including Tax”
• “Shipping Prices” must be set to “Including Tax”
• “Apply Discount on Prices” must be set to “Including Tax”

Tax Calculation for US

• “Tax Calculation Method Based On” should be set to “Unit Price”
• “Catalog Prices” must be set to “Excluding Tax”
• “Shipping Prices” must be set to “Excluding Tax”
• “Apply Discount on Prices” must be set to “Excluding Tax”