CoreBOSBB

Am I right to assume (I browsed around the current code) that the group taxes in an inventory module are not actually stored in the module, but on the individual lines (in 'productInventoryRel')?

And when a inventory module's view is prepared, the group tax is calculated by taking all individual taxes and summing them up?

Yes, that sounds correct. At least as far as I remember. In group tax mode all the inventory lines get the same global tax applied and only one set of values are used

Yes, if I read the code correctly, the sum of all taxes is calculated and stored on the first line. But the group tax is never stored on the 'parent' record, always on the lines.