German taxes and ELSTER, done by an agent

Built from a real filing season: one founder, one small UG, a personal return, every 2025 return and 2026 Voranmeldung filed through Mein ELSTER by an agent with certificate login, plus the Bescheide, Schaetzungsbescheide and Einsprueche that followed. Every trap below cost money or a correction in that run. Personal data has been removed; amounts in examples are illustrative.

This is not tax advice. German tax law changes every year. Every claim tagged (verify) must be checked against the current law (gesetze-im-internet.de, BMF-Schreiben, the current ELSTER form) before it is relied on. When a case involves a foreign entity, a shareholder dispute, a possible Steuerstraftat (any letter that mentions § 371 AO) or real money at stake, recommend a Steuerberater and say why.

Safety rules (non-negotiable)

1. The agent prepares, a human submits or explicitly approves each submission. Pressing "Absenden"/"Übermitteln" is a legally binding declaration in the taxpayer's name (§ 150 AO). Get an explicit go for that form and those numbers, in this session. A general "do my taxes" is not approval to transmit. Approval to send form A is not approval to send form B.
2. Never invent a deduction, a number or a fact. Every line that reduces tax needs a piece of evidence: invoice, bank debit, contract, Eigenbeleg with the debit attached. No evidence, no line. Write [FEHLT: ...] instead of a plausible guess. Bank statements are not invoices.
3. Evidence table per item. For every amount you put in a form: source file, date, counterparty, who the invoice is addressed to, net/VAT/gross, VAT treatment, form line (Kz). Keep it next to the draft. If two sources disagree, stop and report the conflict.
4. Positive proof for assets, not absence of counter-proof. A Vorsteuer claim or a receivable is booked only when it is evidenced (invoice in hand, § 15 Abs. 1 Satz 1 Nr. 1 Satz 2 UStG), not because nothing contradicts it.
5. Secrets never touch logs. Certificate password, PIN, ELSTER login: never in a command-line argument, a log, a prompt, a commit, a chat reply. See references/elster-access.md.
6. Disclose, don't hide. If you know a filed return is wrong, § 153 AO requires correcting it without delay. Use the free-text field (§ 150 Abs. 7 AO, "Ergänzende Angaben") to state what is incomplete and why. A disclosed gap is a correction; an undisclosed one can become a problem.
7. Re-verify state before claiming it. "Filed" means you have a Transferticket and the Übertragungsprotokoll, and "Übermittelte Formulare" went up by exactly one. Not "the button was clicked."
8. Retract loudly. When a later document overturns an earlier conclusion, mark the old file ÜBERHOLT at the top with the reason and point to the current one.

Step 0: triage before any form

Ask or find out, in this order. Most expensive mistakes come from skipping this.

Then size the problems by money at risk and deadline, and work in that order. The late return a founder asks about is often the cheapest item on the list.

Workflow

1. Collect (read-only): ELSTER "Übermittelte Formulare" and Posteingang, bank export with Verwendungszweck per booking (summarised exports merge counterparties and hide what happened), payment-processor export (Stripe balance transactions, not only payouts), vendor invoices downloaded from each vendor portal, contracts, prior Bescheide.
2. Reconcile: bank vs processor vs declared figures, per quarter, to the cent. Reverse-engineer how earlier filings were computed before trusting or "correcting" them.
3. Classify each item (references/vat.md decision table). Mark confidence high/medium/low.
4. Draft the form values with the evidence table. Write the draft to a file.
5. Adversarial review: have a second model or a fresh agent attack the draft ("find every reason not to submit this"). Fix or disclose each finding. In the source run every review round found real defects, including a wrong form line and an invented field value.
6. Fill the form in ELSTER with "Datenübernahme" where offered, run "Alles prüfen", read every error and Hinweis, read back every field from the control state.
7. Human approval of the final numbers and text, explicitly for this form.
8. Submit, then verify (Transferticket, Protokoll PDF saved immediately, counter +1, draft folder empty). Record ticket and timestamp in the working file.
9. Calendar every follow-up: next Voranmeldung, Einspruch deadlines, Vorauszahlungen, Offenlegung, certificate expiry.

Reference files (load only what the task needs)

Ten traps, one line each

1. Anthropic, Cursor and others bill a company without USt-IdNr as a consumer (DE000000000, "VAT Germany 19 %"). That VAT is not deductible Vorsteuer; the reverse charge still applies.
2. EU supplier (Anthropic Ireland, Meta Ireland, Lovable Sweden) → Kz 46/47; third-country supplier (Cursor US, Supabase Singapore, Vercel US) → Kz 84/85. Not interchangeable.
3. Invoice addressed to the founder privately → no Vorsteuer for the company; deduct the gross amount via Auslagenersatz or Einlage with an Eigenbeleg.
4. Einspruch against a Bescheid: 1 month from Bekanntgabe, and Bekanntgabe is the 4th day after posting since 2025 (not the 3rd), rolled to the next working day. Against your own Steueranmeldung the month runs from its receipt (§ 355 Abs. 1 Satz 2 AO).
5. An Einspruch reopens the whole assessment: Verböserung is possible after a warning (§ 367 Abs. 2 AO); withdraw if warned and the downside is bigger.
6. An Einspruch does not stop payment. Apply for Aussetzung der Vollziehung separately.
7. Missing Voranmeldung → Schätzungsbescheid under Vorbehalt; the real filing replaces it. Dauerfristverlängerung is free for quarterly filers and prevents the next one.
8. GewSt for a corporation has no 24,500 EUR Freibetrag; Gewerbeertrag rounds down to 100 EUR.
9. Since 2025 the employer may not apply the Fünftelregelung; it only comes through the ESt return.
10. KSt 1 and GewSt 1 A have no "berichtigte Erklärung" checkbox; mark a correction in free text.