So that every knowledgeable third party (tax auditor, auditor) can get an overview of the accounting within a reasonable period of time, it must meet certain formal requirements.
The principles of proper accounting (GoB) serve this purpose:
The bookkeeping must be clear and straightforward. This includes that the organization of the bookkeeping is appropriate and manageable and that bookings must not be made illegible.
All business cases are to be booked continuously and completely, correctly, on time and in an orderly manner.
Every booking must be based on a receipt.
The bookkeeping documents must be properly stored, with a retention period of 6 years for the documents and a retention period of 10 years for the books (inventories, balance sheets, profit and loss accounts).