What I have learned, in writing.
Practical methodology on international purchasing, product development and trade operations. No textbook theory.
The problem is almost never a missing document
It's two documents saying different things. Customs doesn't read them separately: it compares them. And that's where shipments get stuck.
Two quotes, one 8% cheaper. And you end up paying more
Unit price is the cost line negotiated hardest and the one that matters least. What decides is everything that comes after.
The buyer hasn't paid and the goods are in their warehouse. Who owns them?
Incoterms govern costs, delivery and risk. They don't govern title. And that difference decides whether non-payment leaves you with a claim or a thing.
No customs within the EU. There is still something to prove
Movement is free. The VAT exemption on an intra-EU supply is not: it has to be evidenced. And under EXW the evidence doesn't originate in your hands.
EXW outside the EU: who controls your export evidence
Under EXW the buyer handles clearance. The document you need to justify your VAT exemption ends up in the hands of someone you don't control.