Invoicing by Email – From Trend to Requirement

Electronic invoice delivery has long since ceased to be the exception—it is now the standard. For years, many companies have preferred issuing invoices digitally. The COVID-19 pandemic, in particular, accelerated this development—and with the e-invoicing obligation that came into force on 01/01/2025, one thing is clear: paperless invoicing is here to stay.

According to a 2021 survey by the digital association Bitkom, 32% of companies were already primarily using digital invoice formats, while only 19% still relied on traditional paper formats. These figures are likely to have shifted further in favor of electronic invoicing by now.

But what does this mean in practical terms for sending invoices by email? What qualifies as an e-invoice, which requirements must be met, and how does KLEVERBILL support companies in making the transition to this new era of invoicing in a compliant and efficient way?

1. What is an invoice sent by email?

An invoice sent by email is an electronic invoice transmitted to the recipient via an email system—often as a PDF attachment or via a download link. Like paper invoices, it contains all legally required mandatory information and must be archived accordingly.

However, note: Under the new e-invoicing obligation, a PDF document will no longer be considered an e-invoice. Only structured, electronically processable formats (e.g., XRechnung or ZUGFeRD) qualify as true e-invoices under the new regulation.

2. Mandatory e-invoicing from 01/01/2025: What applies now?

Since January 1, 2025, companies in Germany are required to receive, process, and archive electronic invoices in a structured format for all domestic B2B transactions.

Key deadlines:

• From 2025: Obligation to receive structured e-invoices

• From 2027: Obligation to send only such e-invoices

Simple PDF invoices are now considered so-called “other invoices” and may, from the specified cut-off dates, no longer be used for tax-relevant business transactions—unless a separate agreement has been made between issuer and recipient.

3. Email as a delivery channel: still permitted—with limitations

Despite the new format requirements, email remains a permissible delivery channel. The German federal government confirmed this in September 2024: a standard email inbox is sufficient to receive e-invoices—the invoice is sent in a structured format, no longer as a traditional PDF attachment.

Important: Sending by email is legally compliant only if the invoice contains a structured, machine-readable format—e.g., as an XML file (XRechnung or ZUGFeRD 2.1.1).

4. Benefits of electronic invoicing by email

Digitizing invoice delivery provides substantial benefits for both invoice recipients and invoice issuers:

Benefits for invoice recipients:

• ✅ Lower processing costs

• ✅ Automated capture of invoice data

• ✅ Fewer sources of error & higher data quality

• ✅ Decentralized, location-independent processing

• ✅ Improved cash flow management

Benefits for invoice issuers:

• ✅ Elimination of printing, paper, and postage costs

• ✅ Faster delivery and shorter payment cycles

• ✅ Simplified processes & automated workflows

• ✅ Better traceability and fewer queries

• ✅ Digital operations with lower resource consumption

KLEVERBILL supports both sides—through automated invoice creation, PDF and XRechnung output, digital delivery, and complete archiving.

5. Five key points to observe when sending invoices by email

To ensure invoices sent by email are legally compliant, companies must observe the provisions of Section 14 German VAT Act (UStG):

1. Mandatory information pursuant to Section 14 (4) UStG

Email invoices must also include the following details:

• Name & address of invoice issuer and recipient

• Tax number or VAT ID

• Invoice date & sequential invoice number

• Description of service & delivery/service date

• Net amount, tax rate, tax amount, gross total amount

• Agreed discounts or rebates

2. Consent of the invoice recipient

Until the end of 2024, recipient consent to electronic invoicing was required—for example via terms and conditions or implicitly. Since 2025, no consent is required for e-invoices in an EU-compliant format (e.g., XRechnung). Agreement is still required only for deviating formats.

3. Ensure authenticity, integrity & readability (Section 14 (3) UStG)

The invoice must:

• be verifiably issued by the invoice issuer

• remain readable without alteration

• be traceably linked to the underlying service. This can be achieved, for example, through audit trails, version controls, and tamper-proof archiving—as offered by KLEVERBILL.

4. Tamper-proof electronic archiving

Email invoices must be stored in their original digital form—printouts are not permitted. Archiving systems must be GoBD-compliant: immutable, retrievable, traceable, and machine-readable.

5. Eight-year retention period

Invoices sent by email must be retained for eight years (pursuant to Section 14b UStG), starting at the end of the year of issue. Example: Invoice dated 20/08/2025 → retention until 31/12/2033.

💡 Note: Through the Fourth Bureaucracy Relief Act (BEG IV), the statutory retention period was reduced from ten to eight years as of 01/01/2025—for accounting documents such as invoices and receipts.

6. KLEVERBILL: Your partner for digital invoice delivery & mandatory e-invoicing

With KLEVERBILL, you not only send invoices digitally and automatically—you can do so in structured format today. Our system supports:

• Creation of invoices in ZUGFeRD and XRechnung formats

• Delivery by email with structured file attachment

• Validation of mandatory information before dispatch

• Automated reminder processes for late payments

• Tamper-proof archiving of all invoices (GoBD-compliant)

• Clear dashboard for invoice tracking

🎯 You do not need to worry about legal requirements, technical standards, or archiving—KLEVERBILL handles this for you.

Invoice delivery by email—provided it is in the right format

Sending invoices by email is convenient, cost-efficient, and effective—but since 01/01/2025 it requires compliance with new technical and legal standards. Companies that do not transition to structured e-invoice formats now risk tax disadvantages, rejection by business partners, or even fines.

KLEVERBILL makes the transition straightforward: from correct invoice creation and dispatch through to legally compliant archiving, our software covers all requirements of mandatory e-invoicing—ensuring smooth, digital invoicing processes across your organization.