Almost all EU customers respect the obligation. EU customers who don’t
respect the obligation typically do it as an honest mistake. In that case,
we cancel the order and kindly ask the customer to place the order again
with the correct option.
As you correctly point out, the “VAT option” only covers the main product
and does not apply to other selected options which indeed may modify the
cost. In our case, options only add a minor cost, for example 1 euro for
extra headers. For the sake of simplicity, we accept to loose the VAT on
those extra options, because it has only minor impact on the overall cost.
We still pay VAT on those options, but we simply take it out of our margin.
In the end, we issue a correct invoice with VAT applied correctly to the
product and all options, as well as shipping.
Of course, this is is quirky and I wish Tindie would simply implement a
option to charge VAT automatically, but it works for us for now.