InkVoice — XRechnung & E-Invoicing

Converts between net, tax and gross for a given VAT rate, in either direction.

Give an amount and say whether it is net or gross, and you get all three figures back rounded to the cent. Germany's rates are 19 % (standard) and 7 % (reduced), but any rate from 0 to 100 is accepted, so this also works for an Austrian or French invoice.

Rounding is half-away-from-zero, the convention invoices and tax authorities use, and the three returned figures always reconcile: net plus tax equals gross exactly, with no cent left over from rounding each separately.

What this does NOT do: it does not decide which rate applies to a supply, handle more than one rate at a time, or know anything about reverse charge, intra-community supply or the Kleinunternehmer rules. It is arithmetic, not tax advice.

Checks a German Leitweg-ID — the routing identifier that goes in BT-10 of an XRechnung to a public authority. An invoice to a German public body with a wrong or missing Leitweg-ID is rejected, so this is worth checking before building a document.

It verifies the structure (Grobadressierung of 2 to 12 digits, an optional Feinadressierung of up to 30 alphanumerics, then two check digits) and recomputes the ISO/IEC 7064 MOD 97-10 check digit, the same procedure an IBAN uses. When the check digits are wrong it returns the ones the address parts actually imply, so the value can be corrected rather than merely rejected. It also names the Bundesland the leading two digits point at, or Bund for the federation.

One real limit: the check digit is computed over the address parts with the hyphens removed, which is what KoSIT specifies, so it CANNOT detect a hyphen in the wrong place. '04011000-1234512345-06' and '040110001-234512345-06' both pass. That is the specification's behaviour, not a defect here.

What this does NOT do: it does not confirm that the ID belongs to a real authority or that they are reachable. It checks the number, not the recipient — there is no directory lookup.

Builds a German XRechnung 3.x electronic invoice (EN 16931, CII syntax) from invoice details and returns the XML as text. This is the format German public-sector buyers are legally required to receive, and that many private B2B buyers now ask for.

The EN 16931 business rules are checked before anything is built, and a rejected call comes back naming the rules that failed and the business term (BT-xx) each concerns. The ones worth getting right up front: tax category S requires a rate above 0 %, categories Z, E and AE require exactly 0 %, E and AE additionally require a stated exemption reason (BT-120), and both parties need an email address because XRechnung makes the electronic address (BT-34, BT-49) mandatory. For a public-sector buyer, put their Leitweg-ID in buyerReference (BT-10) — check_leitweg_id will verify it first.

What this does NOT do:

• It does not validate against the KoSIT Prüftool. It applies our reading of EN 16931, which is not the same thing as the Schematron suite a receiving portal runs. Use validate_einvoice for a second look, and the official validator before a deadline.

• It does not produce ZUGFeRD or Factur-X. There is no PDF and no embedded XML — this is a bare XML file.

• It handles ONE tax rate and one tax category for the whole invoice. A document mixing 19 % and 7 % lines is not expressible here.

• It does not send the invoice anywhere, and there is no Peppol.

Nothing is stored: no account, no invoice record, no retained personal data.

Reads an existing electronic invoice and reports what is wrong with it. Accepts XRechnung and ZUGFeRD XML in either EN 16931 syntax — CII (used by XRechnung and ZUGFeRD) and UBL — and reports the syntax and profile it found along with the invoice's key fields, so it also answers "what is this file?".

It checks the rules behind most real rejections: BT-10 buyer reference present, and its Leitweg-ID check digit when it looks like one; BT-34 and BT-49 electronic addresses present; tax category S not used at 0 %; BT-120 exemption reason present for categories E and AE; line amounts summing to BT-106; net plus tax equalling the BT-112 gross; BT-115 amount due matching gross less prepaid; and the due date not falling before the issue date.

What this does NOT do:

• It is NOT the KoSIT Prüftool and is not a substitute for it. It covers the rules that account for most rejections, not the full EN 16931 Schematron suite. A file that passes here can still be rejected by a Rechnungseingangsportal.

• It does not check the XSD schema, so a structurally invalid document may parse here.

• It reads XML only. A ZUGFeRD PDF must have its embedded XML extracted first — pass the XML, not the PDF.

Nothing is stored: the document is parsed in memory and discarded.