The tricky real-world cases of e-invoicing — step by step, with XML examples for UBL and CII.
Credit note (381) or corrected invoice (384)? Type codes per UNTDID 1001, preceding invoice references (BG-3) and sign logic — with UBL and CII examples.
ZUGFeRD profiles explainedZUGFeRD profiles explained: what MINIMUM, BASIC WL, BASIC, EN 16931 and EXTENDED contain, how BT-24 identifies the profile, and which one you should generate.
Negative invoice linesNegative invoice lines in EN 16931 (XRechnung, ZUGFeRD, Factur-X): negative amount and quantity are fine, a negative price is not — plus clean totals math.
Your own PDF design as ZUGFeRD/Factur-XHow to turn a designed invoice PDF into a valid ZUGFeRD/Factur-X e-invoice: PDF/A-3, embedded CII XML, XMP metadata — and the classic pitfalls to avoid.