Effortless E-Invoicing with EGroupware and Univention Corporate Server

As of January 2025, electronic invoicing is now mandatory for B2B transactions in Germany. That means it’s time to get up to speed! The good news for UCS users? There’s no need to invest in additional software—EGroupware, available through the Univention App Center, now includes the E-Invoicing app, a built-in module that fully supports e-invoicing.

Switching to E-Invoices simplifies everything: invoices are sent electronically, received automatically, and seamlessly processed—no more manual steps or paperwork. Instead of relying on printed invoices or static PDFs, all invoice data is structured in a machine-readable format and fed directly into your system. From creation to payment, every step becomes digital and efficient.

With the E-Invoicing app in EGroupware, generating and receiving legally compliant e-invoices couldn’t be easier. The app fully supports the EU standard EN 16931 and automatically generates invoices in XRechnung (XML format) or ZUGFeRD (hybrid PDF/XML). Plus, the PDF layout is fully customizable, allowing you to tailor invoices to your exact needs.

In this article, we’ll show you how to create, send, and receive e-invoices with EGroupware—directly within your UCS environment and without the need for additional tools.

Say goodbye to piles of paper invoices and static PDFs! As of 2025, e-invoices must be issued in a structured electronic format that allows for automated processing. A simple PDF doesn’t count—it’s not considered a legally compliant e-invoice.

For B2B companies, the transition is serious: they must now be able to receive and process e-invoices. However, there are some transition periods to ease the shift:

• In 2025 and 2026, paper invoices and other electronic invoice formats are still allowed—but only if the recipient agrees.
• Starting in 2027, this exception will apply only to small businesses with annual revenues of €800,000 or less (as of 2026).
• EDI invoices (electronic invoices exchanged via an Electronic Data Interchange system) will still be allowed until the end of 2027, as long as the recipient agrees.

Thinking about investing in yet another accounting tool just to comply with e-invoicing regulations? Or worse—getting locked into another costly subscription? If you’re using Univention Corporate Server, you can skip all that. The E-Invoicing app in EGroupware has everything you need built right in, making the transition to e-invoicing simple and seamless.

Development moved fast—once the team found a PHP library for XML-based invoices in late November, they wasted no time. Less than three weeks later, on December 14, the app was ready to go. It’s now available in the latest EGroupware 23.1 release.

Please note: The E-Invoincing app is included in EGroupware’s Enterprise Line (EPL) but not in the Community Edition (CE).

You’ll find the app in EGroupware’s left-hand menu under Invoices. Click it, and you’ll see an organized dashboard displaying all sent and imported invoices. Need to find a specific invoice? Just sort or filter the table by invoice number, date, buyer, seller, or subject—whatever works best for you.

Creating a new invoice is just as easy. Click Add, fill in the subject, billing period, invoice type (currently, trade invoice 380), category, invoice number, and date, and you’re good to go. Already have an e-invoice in XML or ZUGFeRD format? Simply use the Import button to bring it into the system.

As long as an invoice is in draft mode, you can edit any field freely. Once you hit Calculate, it’s locked in. Need to keep track of payment reminders? Use the Notes field to log key details. And here’s a nice extra: Hover over a field label to see its corresponding XML field number.

The lower half of the dialog is where you fine-tune your invoice using several tabs:

• Positions: Add products or services here. Each line item includes standard fields like position, article, description, quantity, price, and VAT. Items are automatically saved to the database for future reuse. Position numbers are assigned automatically but can be adjusted manually if needed.
• Summation: Get a clear breakdown of VAT, discounts, rounding adjustments, and surcharges. Advance payments are also accounted for, and all totals calculate automatically.
• Payment: Enter references, project numbers, contract details, and payment terms, including discounts and due dates.
• Buyer: Select a buyer directly from the EGroupware address book or add contacts manually. You can also input tax and VAT IDs if required.
• Notes: Add comments that can either appear on the invoice or remain for internal use only.
• Links: Attach files, documents, or entries from other EGroupware apps, such as InfoLog or Project Manager, to keep everything connected.

The Invoices app is designed to adapt to your business, not the other way around. In the Admin / App configuration menu, you can fine-tune the settings to match your workflow. Start by defining how invoice numbers are assigned—whether they follow a sequential pattern or a custom format, such as project-based numbering. Even if you’re switching to the app mid-year, it’s seamless: just enter your last used invoice number, and the system will continue from there.

You can also configure standard sellers, contract partners, and custom fields for details like customer numbers or VAT IDs, keeping everything organized. Access control is just as flexible: decide whether team members can select predefined vendors, browse the address book, or edit contact information, ensuring the right level of access for everyone. With these settings, the E-Invoicing app fits smoothly into your existing processes, making invoicing effortless.

The PDF part of your invoice is fully customizable, allowing you to design it just the way you need—even directly in Collabora Online, EGroupware’s built-in office suite. Add your company logo, adjust the layout, and fine-tune the table structure for invoice items to match your preferred format. Meanwhile, the XML section is generated automatically in the standardized format and seamlessly attached to the PDF for ZUGFeRD compliance.

To make things even easier, EGroupware provides a ready-to-use invoice template that you can tweak as needed. All templates are stored in the /templates/invoices directory in .odt format. If you have multiple templates, simply select the right one from the dropdown menu when creating a new invoice.

One of the most powerful features of the app is its flexible use of placeholders. These are text variables enclosed in double curly brackets, such as {{InvoiceId}} or {{InvoiceNo}}. Most placeholders pull data directly from the database, ensuring that invoice details are filled in automatically. But it doesn’t stop there—If-Then-Else conditions can also be used, allowing for dynamic formatting. For example, you can hide empty fields, prevent unnecessary spaces, or insert line breaks only when certain fields contain data. Need a full list of available placeholders? Just check Invoices / Placeholders.

If you frequently create similar invoices, the copy function will be a game-changer. With just one click, you can duplicate an existing invoice and use it as a template for a new one—including all line items, amounts, and recipient details. This makes handling recurring invoices effortless, so you don’t have to start from scratch every time.

No need for extra steps—send invoices directly from the Invoices app via email. Once an invoice reaches the Calculated status, you can select an email template in addition to the ZUGFeRD invoice template. The app then automatically generates an email with the invoice attached, ready for review and sending. This ensures a fast, consistent, and error-free invoicing process.

Receiving e-invoices is just as easy. You can import invoices directly from the EGroupware email app and review the contents. EPL users with the right permissions can do more than just view incoming e-invoices—they can save them directly and even categorize them as incoming invoices for better organization.

With the E-Invoicing app in EGroupware, meeting legal e-invoicing requirements is easy—right within your UCS environment. The app streamlines your invoicing process, saves time, and keeps everything organized. With customizable layouts and support for XRechnung and ZUGFeRD, it adapts perfectly to your business needs—whether you’re a small company or a large organization.

Curious to learn more or give it a try? Reach out—we’d love to hear from you!