Coupons with a fixed value adds up 20% on taxable orders

[dysfunctional]

Hi,

I have just started experimenting with discount coupons with a fixed value, instead of a percentage.

I ship worldwide so obviously I have set up different tax rules depending on the shipping destination. Works great.

However, the latest coupon I sent out had a fixed value of 100 SEK.

On a tax-free order, it works just fine :



But on any order where there is tax involved, it adds 20% to the value of the coupon. And I can't for the life of me figure out why. 25% would kind of make sense because that's the Swedish sales tax (VAT). But I can't understand where 20% is pulled from?



The coupons are automatically created (by mailbeez) and are basically clones of each other. They both say that they're worth 100% when I click on them in admin.

Would really appreciate some advise here, as I have no clue on what I could have overlooked.

Thank you

Best regards

Peter