KleinBooks – German Invoicing & Buchhaltung

Heute Kleinunternehmer, morgen mit Umsatzsteuer — KleinBooks wächst mit.

KleinBooks brings the German business workflow — Angebot → Rechnung (quote → invoice) — directly into your own WordPress admin. No second tool, no monthly SaaS subscription. Start as a Kleinunternehmer (§19 UStG); when your business passes the €25,000 limit, switch to Regelbesteuerung (standard VAT) with one confirmed click and keep working in the same tool.

Free

• Write quotes (Angebote) and convert them to an invoice in one click
• Invoices with the German mandatory fields (§14 UStG) and sequential numbers
• Clean PDF invoices & quotes, sent by email
• Clients, and expenses with categories, recurring costs and receipt upload
• Dashboard and a Taxes overview: revenue, expenses, profit and an estimated tax reserve
• §19 thresholds (€25,000 previous year / €100,000 current year) with a warning before you reach them
• Kleinunternehmer ↔ Regelbesteuerung switch — 19 % / 7 % VAT, net / VAT / gross on invoices and quotes, USt-IdNr, input VAT (Vorsteuer) on expenses and a VAT-owed (USt-Zahllast) overview. Invoices you already issued keep their tax treatment.

Pro

KleinBooks Pro (€59 / year, 14-day free trial) is a separate paid version for when you need to be audit-ready:

• GoBD lock — sent invoices can no longer be changed; corrections go through a proper Stornorechnung (own number) and an optional correction invoice
• DATEV export (EXTF, SKR03/SKR04) for your tax advisor
• USt-Voranmeldung — your quarterly or monthly VAT return figures (Ist or Soll taxation) with PDF
• ZUGFeRD / Factur-X e-invoices — for VAT-registered businesses (issuing becomes mandatory from 2027/2028); Kleinunternehmer are exempt from issuing e-invoices
• AfA / Abschreibung — depreciation of assets

The free version is an invoicing tool: sent invoices stay editable. GoBD lock with Storno is part of KleinBooks Pro.

Source code

The admin app is built with React (@wordpress/scripts). The full unminified source for the compiled bundle in assets/, together with build instructions, is included in the plugin’s src/ directory.