The 19% is the tax. I configured it in "tax is not included". If I configure it "tax is included", the calculation for pricing is not correct:
The final price should be 1,20 EUR. The net price is 1,01 EUR. So I set the pricing of the plan to 1,01 EUR.
If I set the tax included, I have to set the pricing to 1,20 EUR. BUT: In this case in the basket there is only 1,19 EUR. May be it's only marginal, but important. There are other, more expensive plans with the same problem.
If I set the tax included, the basket is not empty but zero after enter the promotioncode. But (of course) I want to have the correct pricing.
I'm sure that I set wrong one detail in the configuration of the plan, in the promotion setting or of the tax setting. But I don't know what.