Much ado about nothing: you absolutely do not need a VAT number on an invoice. And there is zero chance an invoice for a Rust conference would be requalified as "non-business related expense" during a tax audit...
From my experience as a sole proprietor in the EU, yes... you very much need invoices issued with your VAT number for any business expense, or else you get in big trouble. (Also many invoices in EU are e-invoices, which means the tax authorities get updated in real-time, so your tax account gets updated automatically, so you don't have to file taxes -- you just see a balance of what you owe and from what transaction...)
Also... the author's main point is that policies should make sense, not that the loophole is difficult or risky to exploit.
Depends where in the EU maybe? Also depends on the transaction. If the VAT number is on your business expense, you can sometimes avoid paying VAT upfront. Else you can often get your VAT reimbursed later, depending on whether it's a national purchase or an international purchase.
It's sometimes worth it to mention your VAT number as it can save money and/or effort, but I've not heard of it being mandatory, at least not in the Netherlands.
From my experience as a sole proprietor in the EU, yes... you very much need invoices issued with your VAT number for any business expense, or else you get in big trouble. (Also many invoices in EU are e-invoices, which means the tax authorities get updated in real-time, so your tax account gets updated automatically, so you don't have to file taxes -- you just see a balance of what you owe and from what transaction...)
Also... the author's main point is that policies should make sense, not that the loophole is difficult or risky to exploit.