[ElCarsti]

Neither format passed the official KoSIT validator (XRechnung 3.0.2 configuration): 0 of 20 generated test documents were accepted.

XRechnung (UBL):

• use the KoSIT CustomizationID (urn:...#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0)
• emit Party and PostalAddress elements in UBL schema order
• add the fields XRechnung requires: BuyerReference, seller and buyer EndpointID, seller contact (name, phone, email), PaymentMeans (BR-DE-1)
• omit the header DueDate on credit notes

ZUGFeRD (CII):

• emit TradeParty, TradeAddress, TradeTax and header settlement elements in CII schema order
• seller electronic address as URIUniversalCommunication instead of a SEID tax registration; add contact, BuyerReference, due date, payment means

Both, via a shared xml/en16931.ts:

• map the reduced-rate code AA (not in EN 16931) to S; always emit the rate for Z/E/AE; exempt (E) with reason for Kleinunternehmer
• tax number as scheme FC instead of DE-TAX; drop the buyer tax number, which EN 16931 has no field for
• one allowance per VAT category for the document discount (BR-32)
• emit negatively stored credit notes with positive amounts (BR-27)
• payee account from the structured IBAN/BIC settings, falling back to a checksum-valid IBAN in the bank details text

Settings: add company_contact_name (contact person / Ansprechpartner), used as the e-invoice seller contact and falling back to the company name.

Validator: report missing seller VAT ID (BR-CO-26), XRechnung phone/email/ buyer address, a missing IBAN, and VAT that does not match the taxable amount. The latter flags invoices with a document discount, because calculateInvoiceTotals computes VAT before the discount (separate fix).