How to set up a DATEV interface: step by step

DATEV interface: the routes available

DATEV is the software provider that many tax firms in Germany work with. An interface makes sure that data from your software reaches the firm without retyping. There are essentially three routes. First, the file in the DATEV format, usually a CSV file with booking batches that is imported into the firm’s DATEV programs. Second, the digital transfer of receipts and invoice data, for example via DATEV Unternehmen online.

The third route is programming interfaces through which your own or third-party software exchanges data directly with DATEV services. They are more flexible and can be automated, but they generally require registration and activation as well as the cooperation of the tax firm. Which services and terms currently apply changes; we check the current status at the start of a project. Which route fits depends on your software, the invoice volume and the desired degree of automation.

• File in the DATEV format: booking batches as an export, imported by the firm
• Document transfer: handing invoices and receipt images digitally to the firm
• Programming interface: data exchange directly between software and DATEV services

Step 1: Clarify with the tax firm what is to be transferred

Do not begin with the technology but with a conversation with your tax firm. Clarify which data is wanted: outgoing invoices, incoming invoices, payments, cash book or master data of customers and suppliers. Ask about the preferred form of transfer, the rhythm – daily, weekly or monthly – and who does the bookkeeping: the firm or your own team.

Also get the key data of your bookkeeping: adviser and client number, start of the fiscal year, the chart of accounts used (often SKR03 or SKR04) and the length of the ledger accounts. These details belong in the header of the export file and must be correct, otherwise the import routine rejects the data. Also note contact persons at the firm for queries.

Step 2: Map accounts, tax keys and master data

The core of every interface is the mapping: which revenue type in your software is posted to which account? Which tax rate gets which tax key? Which contra accounts apply for payment methods such as bank transfer, credit card or PayPal? You draw up these rules together with the firm. They are the foundation for every later booking landing correctly and automatically.

Special cases need particular attention: invoices abroad, credit notes, partial payments and discounts. Also clarify how customer and supplier numbers are managed so that personal accounts are assigned unambiguously, and which document number serves as the reference. A clean mapping table saves many corrections later and is also an important part of the documentation. The earlier such cases are discussed, the less rework arises in daily operation.

Step 3: Build and set up the interface

With the rules from step 2, the interface is implemented. In the file variant, your software or an upstream program generates the export automatically at the agreed rhythm. Format, mandatory fields, character set, date and number formats must be exactly right. For receipts, the invoice images are linked with the booking data so that the firm finds the matching document for every booking.

For programming interfaces, login, permissions and secure storage of credentials are added. With personal and accounting data in particular, encryption, access restrictions and logging are important. A good implementation also detects duplicate transfers so that an invoice is not booked twice and reports errors instead of silently ignoring them. The documentation of the interface should also be delivered from the start.

Step 4: Test, release and monitor in daily operation

Test first with sample data, better still with a test client that the firm provides. Check samples from all cases: standard invoice, credit note, foreign invoice, partial payment. Compare totals and tax amounts between your software and the accounting. Only when the firm confirms the results does the interface go into live operation. This avoids nasty surprises at the first month-end closing.

In ongoing operation, import logs and notifications on errors help to detect problems early. Record in writing how the transfer works; this supports the procedural documentation under the GoBD, the German principles for the proper keeping and retention of books in electronic form. Also plan for what happens with changes, for example when tax rates, accounts or software change.

Typical pitfalls – and how Nano Concepts helps

Common sources of error are wrong or missing tax keys, inconsistent document numbers, wrongly encoded special characters in names, subsequently changed invoices that are transferred twice, and a lack of agreement with the firm on periods and responsibilities. Most of these problems can be avoided if the mapping and test cases are carefully prepared. Anyone who aligns these points before the start spares themselves later correction entries.

Nano Concepts develops interfaces between shop, inventory system, custom software and DATEV and automates the path from the invoice to the handover. For orientation: manageable connections can fall within the Starter package from €2,500, more extensive automations within the Professional package from €8,000. The exact quote follows the free initial consultation. This guide does not replace tax advice; please clarify accounting questions with your tax firm.