E-invoicing · Quotes · Customers · Appointments · Reminders
Coretool is a web app for self-employed people and small businesses with a German trade licence (Gewerbe). Create invoices as ZUGFeRD / Factur-X PDF or XRechnung XML according to the European standard EN 16931 – no installation, no accounting degree needed.
Since 1 January 2025, businesses in Germany must be able to receive e-invoices for domestic B2B transactions. Issuing e-invoices becomes mandatory step by step: from 2027 for businesses with an annual turnover above €800,000, from 2028 for all others (transition rules under § 14 UStG, German VAT Act). A plain PDF is no longer enough – the invoice needs a structured, machine-readable format.
Coretool was founded by a German master carpenter (Zimmerermeister) who needed a simple tool for his own invoices. It is made for people who would rather do their actual work than paperwork – trades, freelancers and small businesses alike. Full accounting suites like DATEV, lexoffice or sevdesk do much more; Coretool focuses on invoicing and the steps around it.
Features
Enter your company details once – each new invoice is ready in minutes, with logo and automatic VAT calculation.
Upload an existing invoice as PDF – AI reads invoice number, amounts, IBAN and line items. You check the fields and download a ZUGFeRD or XRechnung file.
A GiroCode (EPC QR code) is printed on the PDF. Your customer scans it with their banking app and all payment details are pre-filled.
Create a quote with items, units and prices. Your customer signs it online – one click turns it into an invoice.
Save customers once and pick them from the list. Link appointments to customers and send automatic reminders. Spot overdue invoices and send a payment reminder by e-mail with PDF attached.
Upload an XRechnung (UBL/CII) or a ZUGFeRD/Factur-X PDF and see right away whether it is valid – using the official KoSIT validator. No login, the file is not stored. Error list in German.
Open the validator →Optional add-on for construction trades: a cost-estimating assistant with AI suggestions from a German catalogue of more than 31,000 work items, including on-site measurements with photos. Details (German) →
Pricing
Start for free – no credit card needed. All prices are final prices including 19 % German VAT, cancel monthly.
€9 /month
Add-on cost-estimating assistant: €39/month on its own, €34/month bundled with e-invoicing; Solo customers add it for €25/month. 14-day free trial, cancel monthly.
A hybrid e-invoice format: a readable PDF with an embedded XML data set according to EN 16931. ZUGFeRD 2.x and the French Factur-X are technically the same format. Coretool creates the profile EN 16931.
XRechnung is pure XML (the German CIUS of EN 16931) and is mainly required for invoices to public authorities. Coretool supports both formats.
Not at the moment. The app, the invoices and the support are in German. Coretool is built for businesses that invoice under German rules.
No. Coretool runs in the browser. Data is stored on servers in Germany.
Coretool is developed in Germany by Tim Tüchsen, master carpenter (Zimmerermeister). Contact: support@coretool.de. Full provider details are in the legal notice (Impressum, German).
You will be taken to the registration form on our German site.