Kassenbuch (Cash book)

A Kassenbuch is a daily record of all cash inflows and outflows in a German business. For any watch dealer who accepts cash — even occasionally — keeping a compliant Kassenbuch is a legal obligation under the Abgabenordnung (AO) and the Kassensicherungsverordnung (KassenSichV).

What goes in the Kassenbuch

Every cash transaction, recorded on the day it happens:

• Sales paid in cash. The full sale amount with reference to the underlying invoice.
• Purchases paid in cash (Ankaufsrechnungen from private sellers, supplier payments).
• Cash deposits to the business bank account (Bankeinzahlung).
• Cash withdrawals from the bank (Bankauszahlung).
• Cash refunds, credit notes (Gutschriften).

Each entry needs:

• Date of the cash event.
• Reference to the supporting document (invoice number, receipt number).
• Amount with VAT breakdown where applicable.
• Counterparty name.
• Running cash balance after the entry.

Why the cash book matters

For German watch dealers, cash transactions carry the highest tax-audit scrutiny because:

• High average ticket size makes individual transactions attractive to verify.
• Anonymous-buyer risk. Cash buyers may be subject to money-laundering (GwG) thresholds; transactions over €10,000 in cash trigger explicit identification obligations.
• Margin-scheme interactions. A cash purchase from a private seller under Differenzbesteuerung must be documented with full counterparty details for the tax basis to hold.

A missing or sloppy Kassenbuch is the most common GoBD finding in a watch-dealer audit.

Kassensicherungsverordnung (KassenSichV)

Since 2020, electronic point-of-sale and cash-register systems used in retail must include a technische Sicherheitseinrichtung (TSE) — a certified tamper-evident hardware module that signs each transaction.

For a watch dealer:

• A traditional paper Kassenbuch is still permissible if filled in by hand each day; no TSE required.
• An electronic Kassenbuch software with TSE is required if cash sales are entered into a digital point-of-sale system.
• Bookkeeping software that records cash but is not a point-of-sale system can operate without TSE provided the actual cash receipts have been issued elsewhere (handwritten or pre-TSE receipts).

The dealer's choice depends on cash volume and existing systems. For low cash volume, paper plus manual entry into bookkeeping software is the simplest compliant path.

Storage and inspection

A Kassenbuch is kept for 10 years under GoBD and made available to a Betriebsprüfung on request. Electronic Kassenbücher must be exportable in tax-auditor format.

Related: gobd, differenzbesteuerung, ankaufsrechnung, bill-of-sale.