Section 1
Rule one: Unchangeability (Unveränderbarkeit)
A booking or a receipt, once recorded, cannot be silently altered. If something changes, the original and the change both have to remain visible, with a trail. This is the rule that quietly voids the most bookkeeping. Where firms break it: keeping the books in a plain Excel file. Excel lets anyone overwrite any cell with no record that it happened, which is the opposite of unchangeability. A tax auditor who sees your accounts live in an editable spreadsheet can reject the lot as not GoBD-conform, and then estimate your tax (Schätzung), which rarely goes in your favour. The same problem hits invoices stored as editable Word documents. The fix is not complicated: keep the actual bookkeeping in software that locks entries and logs changes (DATEV, lexoffice, sevDesk and similar are built for this). Excel is fine as a working tool. It is not fine as the system of record.
Section 2
Rule two: Completeness and timeliness (Vollständigkeit, Zeitgerechtheit)
Every business transaction has to be recorded, all of them, and recorded reasonably promptly. You cannot record the ones you feel like and skip the awkward cash sale. And you cannot let a shoebox of receipts pile up for eleven months and reconstruct the year in December. Where firms break it: cash businesses with gaps in the record, and everyone who batches a year of receipts into one frantic session. GoBD expects cash transactions recorded daily (täglich) and other transactions booked without undue delay. The exact tolerance depends on your setup, so confirm the specifics with your Steuerberater, but the direction is clear. Late and partial is a finding.
Section 3
Rule three: The process documentation (Verfahrensdokumentation)
This is the rule almost nobody knows exists, and it is the one auditors increasingly ask for first. You are expected to have a written document describing how your bookkeeping actually works: what software you use, how a receipt travels from arrival to archive, who does what, how digital copies are made and stored, how long things are kept. That document is the Verfahrensdokumentation. Where firms break it: they do not have one at all. Many otherwise-tidy small firms have clean books and no description of how those books get made, and an auditor is entitled to treat missing documentation as a formal defect. You do not need a lawyer to write it. A few pages, honestly describing your real process, is the baseline. Templates exist through DATEV and the tax-advisor associations.
Section 4
The retention footnote worth knowing
GoBD ties into retention periods, and one changed recently. Under the Bürokratieentlastungsgesetz IV, the retention period for accounting vouchers (Buchungsbelege) was shortened from ten years to eight, applying from the start of 2025 to documents whose period had not already expired. Books, inventories and annual accounts stay at ten years, and commercial letters at six. Treat those numbers as the current state to confirm with your advisor, because retention rules move.
Section 5
The fitness test
You are probably breaking GoBD if any of these is true: • Your books or invoices live in an editable Excel or Word file that is your only copy. • You batch receipts and reconstruct months of bookkeeping in one late session rather than recording as you go. • You cannot hand an auditor a written Verfahrensdokumentation describing how your records are made and stored. If you ticked any box, the fix is an afternoon, not a project. Move the system of record into locking software, book as you go, and write the few pages that describe your process. That closes the three findings that cause the most trouble, before an auditor finds them for you.