How does the KOR small-seller scheme work in Magento?

The Kleineondernemersregeling (KOR) exempts Dutch businesses with under €20,000 in annual NL revenue from charging BTW. If you opt in, you don’t charge BTW, can’t reclaim input BTW, and can’t show BTW on invoices, instead invoices must say "vrijgesteld van BTW vanwege de kleineondernemersregeling". In Magento this means: (a) tax class “None” on all products with a 0% rate, (b) invoice template that omits BTW lines and shows the KOR-exemption note, (c) checkout that doesn’t display "incl. BTW" anywhere. If you cross €20,000 mid-year you must register for BTW immediately and start charging from that day, we add a Magento dashboard widget that warns when revenue approaches €18k.