ust-edge-cases

When to use this skill

Use this skill when an agent must decide the VAT treatment of a German invoice that is not a plain domestic 19%/7% B2C sale — i.e. cross-border supplies, small-business invoicing, installment payments, cent-level rounding, or the interaction with e-invoicing rules.

Do not use it for domestic standard-rate B2C sales (covered by skr-journal-mapping), for non-EU third-country supplies, or for tax advice beyond what the sources below support.

Procedure

1. Identify the edge case — reverse charge, small business, intra-EU, OSS, rounding, or e-invoice interplay (see decision table).
2. Apply the rule — pick the Steuerschlüssel and the tax amount.
3. Check the precondition — reverse charge (§13b) needs both a valid customer USt-IdNr. and a supply of services (IT, consulting, construction). §13b covers services, not goods; a goods supply with a buyer USt-IdNr. uses the general intra-EU rule (§4a) at 0% without reverse charge. Article number re-verified 2026-10-09: the UStG was restructured and §3g is now "Ort der Lieferung von Gas, Elektrizität, Wärme oder Kälte" — the reverse-charge article is §13b ("Leistungsempfänger als Steuerschuldner"). Kleinunternehmer requires the prior-year turnover ≤ EUR 20,000 (UStG §19 Abs. 1, read from config). A USt-IdNr. alone is not enough to trigger reverse charge.
4. Generate the journal — use skr-journal-mapping for the accounts and scripts/ust_check.py for the arithmetic.
5. Verify — run scripts/ust_check.py and the verification checklist.

Decision tables

All tables below — edge-case selection, the goods-vs-services split, and the e-invoice interplay — are expanded with worked examples and legal sources in references/procedures.md §1-§6. The condensed rules:

Condensed rules: reverse charge (§13b) shifts the VAT debt to the buyer for intra-community services only; a goods supply to a customer with a USt-IdNr. is 0% under the general intra-EU rule (§4a) and is not reverse charge. Kleinunternehmer (§19, turnover under EUR 20,000) charge no VAT and issue a sonstige Rechnung; invoices under EUR 250 gross are exempt from the issuing obligation. Worked examples and legal sources are in references/procedures.md §1–§6.

Worked examples

Good output — intra-EU IT services, reverse charge

Input: German IT consultancy delivers a SaaS licence to a French customer (USt-IdNr. FR12345678901, valid), EUR 5,000.00 net, supply_type service. Expected output: tax key 06/0, tax amount 0.00, journal debits the customer and credits the service account, and the invoice carries the reverse-charge note "Steuerschuldner ist der Leistungsempfänger (§13b UStG)". scripts/ust_check.py invoice.json → OK VAT treatment valid, 1 lines.

Good output — intra-EU goods, no reverse charge

Input: a German wholesaler ships EUR 12,000.00 of goods to a Dutch customer with a valid USt-IdNr., supply_type goods. Expected output: tax key 06/0, tax amount 0.00, but reverse_charge: false and the note reads "Innergemeinschaftliche Lieferung (§4a UStG)" — no reverse-charge statement. ust_check.py exits 0.

Bad output — reverse charge claimed on goods (the trap)

Input: same goods shipment, but the agent sets reverse_charge: true. ust_check.py exits 2 with: FAIL line 1: reverse charge (§13b) applies to services only — supply_type 'goods' cannot use reverse charge; the general intra-EU rule (§4a) applies The agent must re-issue with reverse_charge: false and the §4a note.

Bad output — Kleinunternehmer charging 19%

Input: a Kleinunternehmer (prior-year turnover EUR 18,000) invoices EUR 300.00 net with tax key 19 and tax amount EUR 57.00. ust_check.py exits 2 with: FAIL line 1: Kleinunternehmer cannot charge VAT (key 19) Fix: re-issue as a sonstige Rechnung with tax key 0, tax amount 0.00.

Bad output — unrounded tax amount

Input: EUR 33.33 net at 19% → stated tax amount EUR 6.3327. ust_check.py exits 2 with: FAIL line 1: tax amount 6.3327 is not rounded to cents (§23 UStDV) Fix: state 6.33 (half-up) and re-run.

Pitfalls from research

The single trap that catches most agents: reverse charge (§13b) is services only — a goods supply to a customer that supplies a USt-IdNr. is taxed at 0% under the general intra-EU rule (§4a), not reverse charge. The article number was re-verified 2026-10-09 (dejure.org: §3g is now the gas/electricity place-of-supply rule). The full list of five traps, with sources, is in references/procedures.md §1–§6.

Verification checklist

• Edge case identified per decision table
• Precondition checked (USt-IdNr., turnover threshold, services category)
• Tax key matches the legal rate
• Tax amount computed and rounded to cents
• scripts/ust_check.py exits 0
• E-invoice interplay documented (e-invoice vs sonstige Rechnung)

Related skills

skr-journal-mapping — the Steuerschlüssel this skill validates are assigned by the journal mapper gobd-archive — tax decisions and ruling evidence are correspondence (6y)

References

• Procedures and worked examples
• Standards and sources
• EVALS