I'm experiencing a very odd behavior in EPiServer Commerce...
Sometimes, very infrequently, an extra tax value is added to the cart. An example is a subscription for a publication for 149kr, which includes 6% sales tax. An additional 6% sales tax is added, for a total of 157,94kr. I haven't been able to reproduce this, neither on the production site, nor in the development environment.
In the code, I leave all tax handling to EPiServer Commerce (and the prices in the (single) market includes tax). I have, however, overriden DefaultTaxCalculator.CalculateShippingTax(ILineItem, IMarket, IOrderAddress, Mone) to always return 0. Since we never add shipping cost for a line item, this shouldn't cause any problems.
I haven't been able to find anything consistent about the (very few) problematic orders. None of the orders contain the same variations (though all of the orders only contain 1 variation), they used different payment methods, they all live in the same country (Sweden), no additional shipping fees have been added.
Has anyone else experienced this?
Any tips on how to try to track this down?
You mean that the sales tax added twice in the total, right? Did you setting the market to included tax?
Which is commerce version you are using? Did you override DefaultOrderFormCalculator to include tax value into order form subtotal?