The e-invoice is already mandatory in Germany’s B2B sector today – and the next stages follow in 2027 and 2028. With Invoice Ninja, I provide you as IT-Service-Commander with a powerful open-source invoicing software – under your own domain, with XRechnung and ZUGFeRD, SEPA direct debit and credit card payments. In this article you’ll learn what matters and how to set yourself up in a future-proof way in good time.
Digitalising your accounting is no longer optional – it’s a legal requirement. Anyone who invoices business customers has to deal with the topic of e-invoicing. At the same time, customers today expect modern, convenient ways to pay. This is exactly where Invoice Ninja comes in – a professional invoicing solution that I, as your regional IT service provider, set up, run and maintain for you.
What is Invoice Ninja?
Invoice Ninja is an established, open-source software for invoicing, quotes, time tracking and payment processing. Worldwide, more than 200,000 self-employed people, freelancers and small and medium-sized enterprises (SMEs) rely on the platform.
The key difference compared to classic cloud services: Invoice Ninja can be self-hosted. This means the software runs on a server that I operate for you or on your own infrastructure – your sensitive invoice and customer data stays under your control and doesn’t leave German or European data centres without your knowledge. For GDPR data protection, that’s a tangible advantage.
The core features include:
- Invoices and quotes – create, customise and send by email
- Recurring invoices and automatic charging (auto-bill) for subscriptions and maintenance contracts
- E-invoices in XRechnung and ZUGFeRD format in line with EN 16931
- Client portal where your customers can view invoices and pay directly
- Payment integration with Stripe, PayPal, GoCardless, Mollie and many more
- Time tracking and project management including Kanban boards
- Dunning with automatic payment reminders
Mandatory e-invoicing in Germany – what’s coming your way
With the Growth Opportunities Act (Wachstumschancengesetz), the legislator decided to gradually introduce mandatory e-invoicing for domestic B2B transactions. Important to note up front: an e-invoice is not simply a PDF. The legislator defines it as an invoice in a structured, machine-readable format that complies with the European standard EN 16931. A scanned document, a Word file or a classic PDF do not meet this requirement.
The timeline at a glance
These deadlines are worth knowing (based on the current guidance from Germany’s Federal Ministry of Finance, BMF):
- Since 1 January 2025 – obligation to receive: Every domestic company in the B2B sector must be able to receive, process and store e-invoices in an audit-proof manner – including small businesses (Kleinunternehmer). A normal email inbox is sufficient as a receiving channel; the recipient’s consent is no longer required for this.
- 2025 and 2026 – transition phase for sending: Paper invoices remain permitted. Classic PDF invoices may still be sent, but only with the recipient’s consent.
- From 1 January 2027 – obligation to issue for larger companies: Anyone whose total turnover in the previous calendar year (2026) exceeded EUR 800,000 must issue domestic B2B invoices as e-invoices.
- 2027 – extended deadline for smaller companies: If your previous-year turnover was no more than EUR 800,000, you may continue to use the transitional arrangement until the end of 2027.
- From 1 January 2028 – mandatory for all: From then on, in principle all domestic B2B transactions must be issued as e-invoices.
What always counts here is the total turnover of the invoice issuer in the previous year – not the recipient’s turnover and not the amount of an individual invoice.
XRechnung and ZUGFeRD – the relevant formats
Two formats have become established in Germany, both of which comply with the EN 16931 standard:
- XRechnung: a pure XML file. This format is used above all in business dealings with public-sector clients and is purely machine-readable.
- ZUGFeRD: a hybrid format. Here the structured XML file is embedded in a PDF/A-3. The result is a single file that is both human-readable (the visible PDF) and machine-readable for accounting software (the embedded XML).
Important exceptions
Not every invoice falls under the obligation. Exceptions include, among others, small-amount invoices up to EUR 250, travel tickets, certain tax-exempt transactions and invoices to private customers (B2C). Small businesses (Kleinunternehmer) also do not have to issue e-invoices themselves – but they must still be able to receive them, and have been required to since 2025.
Please note: This article presents the current situation in general, easy-to-understand terms and does not replace tax or legal advice. For a binding assessment of your individual case, please consult your tax advisor.
How Invoice Ninja meets the e-invoicing requirements
Invoice Ninja comes with e-invoicing built in. In the settings, I activate e-invoicing for you and select the right format – whether XRechnung or ZUGFeRD. If you wish, the structured XML file can be embedded directly into the PDF (ZUGFeRD hybrid), so that your customers receive just a single document that is both human- and machine-readable.
The practical benefit for you: hardly anything changes in your usual workflow. You create your invoice as before – and in the background Invoice Ninja automatically generates the standard-compliant e-invoice document in line with EN 16931. That way you meet the legal requirements without having to get into the technical details.
Because e-invoices are subject to strict validation rules, I set the software up correctly and configure all mandatory details (such as seller identifiers, tax rates and units) so that your e-invoices pass the recipient’s validation cleanly. This helps you avoid rejections and delays in the payment run.
Your own invoicing domain: invoice.yourcompany.com
A particular plus of the self-hosted solution is the professional brand presence. Instead of an anonymous third-party provider in the sender field, your invoicing runs under your own domain – for example: https://invoice.yourcompany.com .
This has several positive effects at once:
- Trust and recognition: When your customers are directed to invoice.yourcompany.com to pay, they see your brand – not that of a third-party provider. This increases willingness to pay and looks professional.
- Consistent corporate design: The client portal and the invoices are designed in your colours, with your logo and your typeface (white-label).
- Data sovereignty: Your data resides on a server that I operate for you or on your own infrastructure – ideally in a German or European data centre.
As your IT service provider, I take care of the entire setup: server, domain connection, SSL encryption, email delivery and ongoing maintenance including updates and backups.
Modern payment methods: get paid faster
A good invoice is one that gets paid quickly. Invoice Ninja can be connected to more than 50 payment providers, so your customers can pay directly from the invoice portal – with one click, without detours.
I set up, among others, the following payment methods for you:
- Classic bank transfer (SEPA credit transfer): The bank details and the payment reference are shown automatically on the invoice. On request, I add a QR code so your customers can trigger the transfer in their banking app without typos.
- SEPA direct debit: Via providers such as GoCardless or Mollie you collect due amounts automatically. This is ideal for recurring invoices, maintenance contracts and subscriptions – once set up, collection happens on time and without manual effort.
- Credit card payment: Via payment service providers such as Stripe or Mollie you accept Visa, Mastercard and other cards. Apple Pay and Google Pay can also be handled this way.
The combination of recurring invoices and automatic collection noticeably reduces your administrative effort and improves your liquidity, because outstanding items become rarer and are settled faster.
The benefits of Invoice Ninja at a glance
- Legally compliant: E-invoices in line with EN 16931 (XRechnung, ZUGFeRD) meet Germany’s e-invoicing requirements.
- Cost control: Open source with no expensive per-user licence fees – you pay for hosting and support, not for every single account.
- Data protection: Self-hosted, GDPR-friendly, data under your control.
- Professional presence: Your own invoicing domain and white-label design.
- Faster incoming payments: SEPA direct debit, credit card and bank transfer directly from the portal.
- Automation: Recurring invoices, auto-bill and automated dunning.
- Scalable: From a single individual to a growing mid-sized company – the solution grows with you.
- Fully managed: Setup, hosting, updates and support from a single source – your regional IT service provider.
Who is this solution for?
Invoice Ninja in my managed variant is a particularly good fit for:
- Self-employed people and freelancers who want a professional, automated invoicing process without a monthly software commitment.
- Skilled-trade businesses and service providers who want to bill recurring invoices and maintenance contracts efficiently.
- Small and medium-sized enterprises (SMEs) that want to implement the e-invoicing requirements in a legally compliant way while retaining data sovereignty.
My all-round service as your IT-Service-Commander
As a regional IT service provider, I take the technology entirely off your hands. You focus on your core business – I make sure your invoicing runs smoothly, compliantly and in a modern way. My service package includes:
- Consulting on the right configuration for your company size and industry.
- Setup of Invoice Ninja on a secure server – operated for you or on your own infrastructure, on request under your own invoicing domain such as invoice.yourcompany.com
- Configuration of e-invoicing (XRechnung/ZUGFeRD) including the correct mandatory details.
- Integration of payment methods – bank transfer, SEPA direct debit and credit card.
- Individual design in your corporate design (white-label).
- Ongoing operation with updates, backups, monitoring and personal support.
Frequently asked questions about e-invoicing with Invoice Ninja (FAQ)
Do I have to issue e-invoices as a small business (Kleinunternehmer)?
No. Small businesses are exempt from the obligation to issue. However, since 2025 they must be able to receive and process e-invoices.
Is a PDF an e-invoice?
No. A classic PDF is an “other invoice”. A genuine e-invoice comes in a structured format compliant with EN 16931, for example as XRechnung (XML) or ZUGFeRD (PDF with embedded XML).
Can Invoice Ninja handle both XRechnung and ZUGFeRD?
Yes. Both formats are supported. With ZUGFeRD, the XML file can be embedded directly into the PDF, so your customers receive a single document.
Does my data stay in Germany?
With the self-hosted solution, you determine the server location. I run Invoice Ninja for you in a GDPR-friendly way, on request in a German or European data centre or directly on your own infrastructure.
Can I have recurring invoices collected automatically?
Yes. In combination with SEPA direct debit (e.g. via GoCardless or Mollie), due amounts are collected automatically – ideal for subscriptions and maintenance contracts.
From when do I have to send e-invoices?
It depends on your previous-year turnover: companies above EUR 800,000 from 2027, everyone else from 2028 at the latest. You have been required to be able to receive e-invoices since 2025.
Conclusion: get future-proof now
Mandatory e-invoicing has long been here – the obligation to receive already applies, and the next stages follow in 2027 and 2028. At the same time, this is an opportunity to modernise your entire invoicing. With Invoice Ninja you get a powerful, open-source solution that meets the legal requirements under EN 16931, runs under your own domain and enables modern payment methods such as SEPA direct debit and credit card.
As IT-Service-Commander, I set everything up for you and manage ongoing operation – hosted for you or on your own infrastructure. That way you are prepared in good time, save time in your day-to-day work and leave a professional impression with your customers.
Get in touch – I’ll be glad to advise you on your individual e-invoicing solution.
