ED09 - AO Fundamentals: Taxation Procedure, Deadlines, Voluntary Disclosure

Problem

The Fiscal Code (AO) is the foundation of German tax law - but in the SME sector it is largely unknown:

"AO? Never heard of it." - many entrepreneurs don't know the AO, even though they work according to it every day (bookkeeping, deadlines, audits)
Missed deadlines - assessment periods, filing deadlines, and limitation periods are missed because nobody monitors them
Estimates as a threat - § 162 AO (estimate) is perceived as an abstract threat, without clarity on when it takes effect
Voluntary disclosure as a last resort - § 371 AO (voluntary disclosure) is known as the "emergency brake", but the requirements are complex
External audits as a bogeyman - § 193 AO (external audit) is feared, without clarity on what it actually means
No deadline monitoring - deadlines are in the calendar, but nobody automatically warns before they expire

Key message

The AO governs the taxation procedure - and GitCover makes the obligations resulting from it machine-readable and automatically monitorable:

Deadlines as a Git artifact - checks/FRISTEN_CHECK.md with auto-warning (see ED08)
External audits as an Evidence-Package - Z3/Z3+ export (see ED05)
Avoiding estimates through GoBD compliance - complete, traceable, immutable bookkeeping (see ED05–ED08)
Voluntary disclosure as a last resort - documented in the journal if GoBD compliance cannot be established

Compliance by Design: The AO obligations are not fulfilled through subsequent audits, but through **structural ** Git-native compliance - deadline check, Evidence-Packages, GoBD-compliant bookkeeping.

The Fiscal Code (AO) - Overview

%%{init: {'theme':'base','themeVariables':{'primaryColor':'#FBFAF7','primaryTextColor':'#0F1B33','primaryBorderColor':'#6B7280','lineColor':'#6B7280'}}}%% flowchart TD AO["Abgabenordnung (AO)"] AO --> BV["Besteuerungsverfahren
§§ 78–133"] AO --> FB["Festsetzungs- und
Feststellungsverfahren
§§ 155–217"] AO --> AP["Außenprüfung
§§ 193–203"] AO --> SZ["Sanktionen
§§ 152, 162, 370, 379"] BV --> AN["Anmeldungen
(LStA, UStA, SV)"] FB --> FF["Festsetzungsfristen
§ 169 AO"] AP --> Z["Datenzugriff
Z1/Z2/Z3 (§ 147 Abs. 6)"] SZ --> VS["Verspätungszuschlag
§ 152 AO"] SZ --> SC["Schätzung
§ 162 AO"] SZ --> ST["Steuerstrafverfahren
§ 370 AO"] style AO fill:#0F1B33,stroke:#0F1B33,color:#FBFAF7 style BV fill:#DBEAFE,stroke:#1D4ED8,color:#0F1B33 style FB fill:#DBEAFE,stroke:#1D4ED8,color:#0F1B33 style AP fill:#DBEAFE,stroke:#1D4ED8,color:#0F1B33 style SZ fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style AN fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style FF fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style Z fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style VS fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style SC fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style ST fill:#FDBA74,stroke:#C2410C,color:#0F1B33

AO area	Sections	SME relevance
Taxation procedure	§§ 78–133	Returns (LStA, UStA), duties to cooperate
Assessment procedure	§§ 155–217	Assessment periods (§ 169), estimates (§ 162)
External audit	§§ 193–203	Business audit, data access Z1/Z2/Z3
Sanctions	§§ 152, 162, 370, 379	Late-filing surcharge, estimates, tax criminal proceedings
Bookkeeping	§§ 140–147	GoBD basis (see ED05–ED08)
Voluntary disclosure	§ 371	Emergency brake for tax evasion

Deadlines in the taxation procedure

Monthly deadlines

%%{init: {'theme':'base','themeVariables':{'primaryColor':'#FBFAF7','primaryTextColor':'#0F1B33','primaryBorderColor':'#6B7280','lineColor':'#6B7280'}}}%% timeline section Lohnsteuer 10. : Lohnsteuer-Anmeldung § 41a EStG +5T : elektronisch +5 Tage section Umsatzsteuer 10. : Umsatzsteuer-Voranmeldung § 18 UStG section Sozialversicherung 3-letzter : SV-Beitragsnachweis § 23 SGB IV

Annual deadlines

%%{init: {'theme':'base','themeVariables':{'primaryColor':'#FBFAF7','primaryTextColor':'#0F1B33','primaryBorderColor':'#6B7280','lineColor':'#6B7280'}}}%% timeline section Steuererklärungen 31.07. : ESt / KSt / USt-Erklärung verl. : verlängert durch StB section Lohnsteuer-Bescheinigung 28.02. : Lohnsteuer-Bescheinigung § 41b EStG

Assessment periods (§ 169 AO)

%%{init: {'theme':'base','themeVariables':{'primaryColor':'#FBFAF7','primaryTextColor':'#0F1B33','primaryBorderColor':'#6B7280','lineColor':'#6B7280'}}}%% timeline section Regelfall 4J : Regelfrist § 169 Abs. 2 Nr. 2 AO section Erschwerung 5J : Bei leichtfertiger Verkürzung 10J : Bei Steuerhinterziehung

Deadline type	Deadline	Legal basis	GitCover monitoring
Wage tax return	10th of the following month (+5 days electronic)	§ 41a EStG	`FRISTEN_CHECK.md` + auto-warning
VAT advance return	10th of the following month	§ 18 UStG	`FRISTEN_CHECK.md` + auto-warning
Social security contribution statement	third-to-last banking day	§ 23 SGB IV	`FRISTEN_CHECK.md` + auto-warning
ESt/KSt/USt return	31 July (extended by tax advisor)	§ 149 AO	`FRISTEN_CHECK.md`
Wage tax certificate	28 February of the following year	§ 41b EStG	`FRISTEN_CHECK.md`
Assessment period (regular)	4 years	§ 169 Abs. 2 Nr. 2 AO	Retention period tracking
Assessment period (understatement)	5 years (reckless) / 10 years (intentional)	§ 169 Abs. 2 Nr. 1/2 AO	Retention period tracking

Practical tip: The deadline check (checks/FRISTEN_CHECK.md) is maintained as a Git artifact and updated on every commit. The auto-warning (see ED08) warns 14 days before an authority deadline expires. This way, no missed deadline is overlooked anymore - and § 152 AO (late-filing surcharge of up to 25,000 EUR) is avoided.

Estimates (§ 162 AO) - and how Git avoids them

%%{init: {'theme':'base','themeVariables':{'primaryColor':'#FBFAF7','primaryTextColor':'#0F1B33','primaryBorderColor':'#6B7280','lineColor':'#6B7280'}}}%% flowchart LR S["Schätzung § 162 AO"] S --> G1["Grund 1:
Daten nicht verwertbar
(unvollständig, verändert)"] S --> G2["Grund 2:
Buchführung nicht GoBD-konform"] S --> G3["Grund 3:
Unternehmer liefert keine Auskunft"] G1 --> R["FA schätzt die Besteuerungsgrundlagen
oft zuungunsten des Unternehmers"] G2 --> R G3 --> R R --> B["Beweislastumkehr:
Unternehmer muss Schätzung widerlegen
bei fehlenden Daten kaum möglich"] G["GitCover-Lösung"] G --> V["Vollständige GoBD-konforme Buchführung"] G --> N["Nachvollziehbarkeit (Rz. 146)"] G --> P["Nachprüfbarkeit (Rz. 147)"] G --> E["Evidence-Package (Z3+)"] V --> AV["Schätzung vermieden"] N --> AV P --> AV E --> AV style S fill:#0F1B33,stroke:#0F1B33,color:#FBFAF7 style G1 fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style G2 fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style G3 fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style R fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style B fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style G fill:#10A987,stroke:#0A7F5C,color:#FBFAF7 style V fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style N fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style P fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style E fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style AV fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33

An estimate is the consequence - not the penalty: § 162 AO is not a penalty, but a consequence of unusable bookkeeping. Anyone who keeps GoBD-compliant books (ED05–ED08) makes estimates unnecessary - the auditor can read the tax bases directly from the repo.

External audits (§ 193 AO) - and how Git makes them easier

Audit type	Trigger	Frequency	GitCover support
Regular audit	Size/revenue of the company	3–5 years	Evidence-Package (Z3+), Static-Web
Audit for cause	Suspicion, tips, random sample	If there is cause	git bundle, `git log`, `git grep`
Follow-up audit	Anomalies in the preliminary audit	After the regular audit	Complete history traceable

Practical example: The auditor announces an external audit. The entrepreneur (E1) generates a Tenant Evidence Package (git bundle + Static-Web + Manifest) for the audit period. The auditor receives the USB stick, opens index.html (Z3+) or git clone (Z3), and can navigate all bookings, receipts, process documentation, and sidecars - offline, without IAM, without a cloud account.

Voluntary disclosure (§ 371 AO) - the emergency brake

%%{init: {'theme':'base','themeVariables':{'primaryColor':'#FBFAF7','primaryTextColor':'#0F1B33','primaryBorderColor':'#6B7280','lineColor':'#6B7280'}}}%% flowchart TD H["Steuerhinterziehung § 370 AO
entdeckt"] H --> SA["Selbstanzeige § 371 AO
möglich?"] SA -->|ja, wenn| V1["1. Vollständig
alle verkürzten Steuern"] SA -->|ja, wenn| V2["2. Unverzüglich
nach Entdeckung"] SA -->|ja, wenn| V3["3. Kein Prüfungsbeginn
noch keine Prüfung angekündigt"] SA -->|ja, wenn| V4["4. Nachzahlung
innerhalb angemessener Frist"] V1 --> W["Wirkung:
Straffreiheit (§ 371 Abs. 3)"] V2 --> W V3 --> W V4 --> W SA -->|nein| ST["Steuerstrafverfahren
§ 370 AO
Freiheitsstrafe bis 5 Jahre"] style H fill:#0F1B33,stroke:#0F1B33,color:#FBFAF7 style SA fill:#FDBA74,stroke:#C2410C,color:#0F1B33 style V1 fill:#DBEAFE,stroke:#1D4ED8,color:#0F1B33 style V2 fill:#DBEAFE,stroke:#1D4ED8,color:#0F1B33 style V3 fill:#DBEAFE,stroke:#1D4ED8,color:#0F1B33 style V4 fill:#DBEAFE,stroke:#1D4ED8,color:#0F1B33 style W fill:#D1FAE5,stroke:#0A7F5C,color:#0F1B33 style ST fill:#FDBA74,stroke:#C2410C,color:#0F1B33

GitCover and voluntary disclosure: When an entrepreneur discovers that they have understated taxes (e.g., a forgotten VAT return), they can document the voluntary disclosure in the journal - with role: "GF", source: "E1", and a commit with a rationale. Completeness (§ 371 Abs. 1) is evidenced by the repo: all understated taxes are traceable. Immediacy is documented by the uuidV7 timestamp in the journal entry.

Caution - voluntary disclosure is complex: The requirements for a valid voluntary disclosure are strict. If anything is unclear, always consult a tax advisor or a lawyer specialized in tax law. GitCover documents the voluntary disclosure - but it does not replace legal advice.

Sanctions for AO violations

Sanction	Legal basis	Requirement	Amount
Late-filing surcharge	§ 152 AO	Missed deadline for returns	up to 25,000 EUR
Estimate	§ 162 AO	Unusable bookkeeping	often to the disadvantage
Penalty for delay	§ 146 Abs. 2c AO	Outsourcing without approval	2,500–250,000 EUR
Administrative offense	§ 379 AO	Violation of record-keeping obligations	up to 50,000 EUR
Tax criminal proceedings	§ 370 AO	Intentional tax evasion	imprisonment of up to 5 years
Voluntary disclosure	§ 371 AO	Exemption from punishment if complete	- (repayment + 6% surcharge)

Risk leverage: Each of these sanctions is avoided or mitigated through GoBD-compliant use of Git - the deadline check prevents late-filing surcharges, GoBD-compliant bookkeeping prevents estimates, Evidence-Packages facilitate external audits, and the repo itself is the best proof of proper order.

Risk leverage

Today (cheap)	Tomorrow (audit-proof)	Risk mitigated
Deadline check as a Git artifact	Missed deadlines avoided	Late-filing surcharge § 152 AO
GoBD-compliant bookkeeping	Estimate § 162 AO avoided	Estimate to the disadvantage
Evidence-Package (Z3+)	External audit facilitated	Penalty for delay § 146 Abs. 2c
`git log` as evidence	Proper order proven	Administrative offense § 379 AO
Voluntary disclosure in the journal	Completeness + immediacy documented	Tax criminal proceedings § 370 AO

Harness requirement (preview)

Derivable from ED09:

ID	Requirement	Priority
FA-4.1	Deadline check file (`checks/FRISTEN_CHECK.md`)	MUST
FA-4.2	Deadline entries with date, type, Tenant, receipt reference	MUST
FA-4.3	Auto-warning for deadlines under 14 days	SHOULD
FA-4.5	Follow-up marker for assessment notices/documents	MUST
FA-6.5	10-year retention via Evidence-Packages	MUST
FA-6.7	Static-Web generator for period-end closing (Z3+)	SHOULD
FA-12.5	Interface error logging (errors as repo events)	MUST

The complete list of requirements in Harness-Anforderungen.md.

Sources

AO (§§ 78–133 - taxation procedure, § 146–147 - bookkeeping/retention, § 152 - late-filing surcharge, § 162 - estimate, § 169 - assessment periods, § 193–203 - external audit, § 370 - tax evasion, § 371 - voluntary disclosure, § 379 - administrative offense)
EStG (§ 41a - wage tax return, § 41b - wage tax certificate)
UStG (§ 18 - VAT advance return)
SGB IV (§ 23 - social security contribution statement)
GoBD (BMF letter, Rz. 146 - traceability, Rz. 147 - verifiability)
AFJD/agents/ (anonymized) - SSoT concept with deadline check, external audit preparation

Source topology and CDN reference links

Role	Location	Purpose
Primary / SSoT	git.gitcover.org/GCC	Canonical storage (GPG-signed, versioned)
Public OSS Mirror / CDN	codeberg.org/gitcover-commons	Read-only mirror; FLOSS discovery
Community Hub	github.com/gitcover-commons	Issues & Discussions; source code reference on Codeberg

Note: This mapping of sources, mirror, and community hub reflects the current state and may change. Please check the respective canonical source on gitcover.org for the current state.