KleinBooks – Rechnungen & E-Rechnung für Kleinunternehmer & Selbstständige
by opskleinbooks
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 in three templates (DIN 5008 layout that fits a window envelope), sent by email
- Your own e-mail texts for invoices, quotes and Stornorechnungen — shown and adjustable before every send
- 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 (€69 / year incl. 19% German VAT, i.e. €57.98 net; the VAT follows your country, businesses with a VAT ID pay net; 14-day free trial without credit card that ends automatically) is a separate paid version that adds the bookkeeping side. It is sold by our authorised reseller (Merchant of Record) Freemius, Inc.:
- 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.
Screenshots
Dashboard: invoiced revenue, open and overdue invoices, expenses and your Kleinunternehmer limit at a glance.
Invoices with automatic numbers and clear statuses: draft, open, overdue, paid, cancelled.
Clean invoice PDF with the German mandatory details (§14 UStG), ready to send by email.
Quotes (Angebote) that turn into an invoice in one click.
Expenses by category, with recurring costs and reminders for missing receipts.
Taxes: income by payment date, profit, tax reserve and the three §19 limits.
Settings: Kleinunternehmer (§19) or Regelbesteuerung (VAT), switched with one confirmed click.
"Mark as paid" asks when the money arrived – the payment date decides in which year the income counts.
Template & e-mail: three invoice templates and your own e-mail text, with a preview of the PDF and the e-mail.