GoBD-Compliant Cash Book in Allied Health Practices: Requirements, Sequential Numbers and Receipt Obligations

What the GoBD Require of a Cash Book

The GoBD define the cash book as a daybook in which all cash receipts and cash payments must be recorded completely, correctly, promptly and in order. 'Promptly' means: at the latest on the following working day. Receiving a cash payment on a Friday and posting it on Monday is already a grey area; waiting several days is a clear breach.

Crucially, the cash book must be self-contained and immutable. No entry may be deleted or overwritten after the fact. Every error is corrected exclusively by a cancellation entry - a counter-entry that references the original document number. This immutability is not a bureaucratic detail; it is the core of the audit concept: inspectors must be able to trace how every cash balance arose.

Electronic point-of-sale systems have been subject to the additional requirements of the Cash Register Security Regulation (KassenSichV) - including a certified technical security module (TSE) - since 1 January 2020. Software-only cash books without a physical till, as many small practices use, are not directly covered by the TSE rules, but they remain fully subject to all other GoBD requirements.

A common misconception: the GoBD apply not only to businesses that are required to keep double-entry accounts. Freelancers and income-surplus-calculators - the legal form used by many allied health practices - must also record cash transactions and retain those records in GoBD-compliant form as long as they have any cash income at all.

Sequential Numbering: Unbroken, Traceable and Separate per Till

The cornerstone of every GoBD-compliant cash book is the continuous, unbroken sequential document number. Every receipt receives a unique number assigned chronologically; there must be no gaps. A missing number or a duplicate is treated by the tax authority as evidence of manipulation - even if the cause was simple human error.

Practices with multiple locations or multiple tills must maintain a separate, independent number sequence for each till. Mixing sequences from different tills is treated as a serious bookkeeping error.

Numbering must be unique within a financial year. A recommended format is YYYY-NNNNN, e.g. 2026-00001, 2026-00002 and so on, resetting at the start of each new financial year. Cancellation entries also receive their own sequential number - they are not exempt from the numbering requirement.

• ✓Sequential numbering with no gaps or duplicate numbers
• ✓A separate number sequence per till and per location
• ✓Recommended format: YYYY-NNNNN (e.g. 2026-00142)
• ✓Cancellation entries receive their own sequential number
• ✓Year-end reset of the counter is permitted and standard practice

Cancellation Instead of Deletion: the GoBD Correction Principle

The most common mistake in small-practice cash bookkeeping: an incorrect entry is simply deleted or overwritten. The GoBD strictly forbid this. Every entry is an immutable fact in the bookkeeping history. An incorrectly posted cash receipt - say because the amount was mistyped or the wrong patient was assigned - must be corrected by an explicit cancellation entry.

The cancellation entry contains the reverse amount, today's posting date, a clear description such as 'Cancellation of document 2026-00089' and a new sequential number. Immediately afterwards comes the correct posting as a new, independent entry - again with its own sequential number.

This three-step process (original entry, cancellation entry, corrected entry) increases the total number of lines but creates the unbroken audit trail tax inspectors expect. Practice management systems that enforce this principle technically - preventing any after-the-fact alteration of entries - build GoBD compliance into the system itself, which is treated as a strong quality indicator during an audit.

The Daily Closing Balance and Cash-Count Requirement

The GoBD require that the physical cash balance be reconciled with the book balance every day. This cash count must be documented. In practice: at the end of every business day on which cash moved, the actual notes and coins in the till are counted, recorded and compared with the calculated closing balance from the cash book.

Any difference must be explained or posted as a cash discrepancy entry. Repeated, unexplained differences are a warning signal for auditors. Especially critical: the cash balance must never be negative. A negative balance is physically impossible - cash cannot fall below zero - and immediately signals to the tax authority that entries are missing or the cash book does not reflect reality.

The daily close must be locked in the system - meaning it may not be altered afterwards. The GoBD immutability principle applies here too. Many practice management systems offer an explicit daily-close function that freezes all that day's entries. This should be used consistently.

• ✓Daily cash count: count and document the actual physical cash balance
• ✓Reconcile with book balance; explain or post any differences as a cash discrepancy
• ✓The cash balance must never be negative
• ✓Lock the daily close so it cannot be altered (system-level freeze)
• ✓Perform on every day cash transactions take place, without exception

Receipts: Requirements and Retention

Every cash book entry must be backed by a receipt. For cash payments from patients this is typically a numbered receipt (duplicate retained by the practice) or an internal voucher for receipts for which no external document exists. Internal vouchers must include the date, amount, purpose and the signature of the responsible person.

Paper receipts may be digitised and then destroyed, provided the digitisation process meets GoBD requirements: the scanned image must faithfully reproduce the original, the process must be documented (procedural documentation), and the digital version must be stored immutably. Simply scanning to PDF without procedural documentation is not GoBD-compliant.

The retention period for cash books and all associated receipts is ten years (Section 147 German Fiscal Code). The period runs from the end of the calendar year in which the last entry was made. During the entire retention period all records must be machine-readable and exportable in GDPdU-compatible format - archiving as unsearchable image files is insufficient.

• ✓Every entry is backed by an external receipt or a properly prepared internal voucher
• ✓Digitisation is permitted when procedural documentation exists and originals are faithfully scanned
• ✓Retention period: 10 years from the end of the year in which the record arose (Section 147 AO)
• ✓Machine readability and GDPdU export must be guaranteed for the entire retention period

Specifics for Allied Health Providers: Self-Billing, Co-Payments and the Cash Till

Allied health practices differ from most other businesses in one important respect: the vast majority of income arrives not as cash but as bank transfers from statutory or pension insurers (Section 302 Social Code Book V) or as invoices to private patients. Cash payments arise mainly from statutory co-payments (currently 10% per prescription, minimum EUR 5, maximum EUR 10) and from private services or retail sales.

Co-payments are particularly tricky to handle: the amounts are small, they arise multiple times daily and are collected by different members of staff. Without a clear process - who collects what, when, with which receipt - gaps in the cash book appear quickly. Best practice is to issue numbered receipt books to each staff member and reconcile collected co-payments against the cash book at the end of each shift.

Practices that bill the insurers directly under Section 302 SGB V (without a billing centre) must keep insurer transfers strictly separate from cash income. Reimbursements from insurers are bank movements, not cash receipts - they belong in the general ledger, not in the cash book. Mixing the two is a classic audit finding.

Procedural Documentation: the Under-Estimated GoBD Obligation

Less well-known but equally mandatory: the GoBD require procedural documentation describing how cash bookkeeping is organised in the practice. This documentation must allow any person familiar with bookkeeping to understand how cash receipts are recorded, how errors are corrected, how receipts are archived and who has which access rights in the system.

The document does not need to be long, but it must be complete. It typically comprises a general description of the process, a technical description of the system in use and a description of controls (e.g. who reviews the daily close). The complete absence of procedural documentation is itself a formal GoBD breach.

For practices that handle cash bookkeeping through practice management software, the provider should supply a technical system description that can be incorporated into the procedural documentation. The practice then adds its own organisational procedures. This document must be retained alongside the bookkeeping records - again for ten years.

• ✓Procedural documentation is a GoBD requirement, not optional
• ✓Content: process description, system description, controls, roles and responsibilities
• ✓Practice management software providers should supply a technical system description
• ✓Retain alongside bookkeeping records for 10 years

What Tax Inspectors Actually Examine During an Audit

Tax audits in allied health practices are less frequent than in the hospitality sector, but they do occur - and cash bookkeeping is regularly a focal point. Auditors typically request a machine-readable GDPdU/GoBD export of all cash book data and analyse it with evaluation software. Statistically conspicuous patterns stand out immediately: missing sequence numbers, unusual posting times, clusters of round amounts or recurring discrepancies.

A particularly critical audit test is Benford's Law analysis of cash receipts. Natural number sequences follow Benford's Law (leading digit 1 occurs far more often than 9). Deviations statistically point to interference with the data and trigger deeper investigation.

The most common audit findings: missing or unattributed receipts, negative cash balances on individual days, missing daily closing entries, after-the-fact alterations to entries (visible through audit logs in modern systems) and absent procedural documentation. Taken together, these deficiencies can lead the tax authority to declare the bookkeeping non-compliant and apply a blanket addition to income - often substantially above the actual shortfall.

• ✓A machine-readable GDPdU/GoBD export file must be available on request
• ✓Statistical analyses (Benford's Law, chi-squared) detect patterns in manipulated data
• ✓Common findings: negative balances, missing receipts, missing daily closes
• ✓Formal deficiencies can trigger income estimation well above the actual error