E-invoicing answers
Straight answers to the questions people actually ask about European e-invoicing, each one distilled from the reference documentation it links to.
These pages answer a question rather than document a feature. They are short, they stand on their own, and each one hands off to the reference page that carries the detail. If you are evaluating Beliq rather than the topic, the FAQ on beliq.eu answers the product questions instead.
Validation
The three layers, what each catches, and why not every format has all three.
What happens when an e-invoice fails validation?Reading a rule ID, a severity and an XPath, and which failures actually block you.
How do I validate an e-invoice from code?The request, the fields worth branching on, and the failures that are not your invoice.
Why does the same invoice pass one validator and fail another?Four causes, only one of which is your file.
Evidence and versions
Two fingerprints, three checks, and the ceiling of what they prove.
Which version of the rules is my invoice checked against?The two version axes, and which one you control.
Formats
One format, two labels, and the single profile that differs.
Is XRechnung just EN 16931 for Germany?What a CIUS is, and what Germany adds on top.
UBL or CII: which XML syntax do I need?Usually the target format decides for you.
Can an e-invoice live inside a PDF?What a hybrid actually is, and why a plain PDF is not an e-invoice.
Mandates
Why there is no single European date, and where the current ones stand.
What does the French mandate require of my invoicing software?The perimeter, the format, the routing, and the invoice-number trap.