At today's call we identified the need to include a TaxTotal/CalculationSequenceNumeric to accommodate tax calculations where a particular tax scheme is applied to an amount produced by a preceding tax scheme calculation.

Examples found in Australia: For wine, a wine equalization tax is added first and then GST (VAT) on top of that. And reverse for cars, the GST is added first and then a luxury car tax is added on top of that for new cars.

We already have a CalculationSequenceNumeric in the TaxSubtotal, but in the above example, the different taxes belong to different tax scheme and therefore would belong to different TaxTotals.

https://lists.oasis-open.org/archives/ubl/201904/msg00034.html