TARGET_SYSTEM: datev-rewe datev-rewe-longtoken Your program for exchanging receipts, data, and documents between companies and tax advisors.
ReadCreateUpdateDeleteWebhook
Accounts
Async task
Bank accounts
Bills
Bill lines
Booking proposals
Contacts
Customers
Credit notes
Dimensions
Expenses
Files
Goods receipts
Goods receipt lines
Invoices
Invoice lines
Items
Journals
Journal entries
Offers
Offer lines
Open items
Payments
Payment terms
Projects
Purchase orders
Purchase order lines
Sales orders
Sales order lines
Suppliers
Tax rates
Transactions
Units
Users
Vendor credits
= Supported by Maesn
= Not supported by Maesn at this time
= Not supported by DATEV Rechnungswesen

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What is DATEV Rechnungswesen

DATEV Rechnungswesen is an application for accounting used by small- and medium sized companies. It does not belong to DATEV’s suite of online applications, meaning that it is essentially an on-prem application that can be hosted by a provider or on your own server. Despite this, there is one service available that can be used to transfer a limited set of data to DATEV Rechnungswesen. All other data, such as files and booking proposals need to be transfered via DATEV Unternehmen Online. DATEV infrastructure

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How to connect to DATEV Rechnungswesen

It is possible to create journal entries, suppliers and customers directly in DATEV Rechnungswesen through maesn’s API.
1

Configure your integration in the maesn API

Since maesn has partnered with DATEV to help bring software companies to successful integrations quickly, the entire setup process is executed with maesn. There is no need to book consulting packages with DATEV.Everything from setting up client credentials and getting sandbox access, to getting your integration approved by DATEV is done by maesn.
  • Get in touch with your contact person at maesn to configure the API and DATEV OAuth client.
If you are not sure who your technical contact is, do not hesitate to reach out to us.
2

Testing your integration in a production environment

To test your integration against a live production environment is both recommended and necessary, before offering the functionality to your customers.You will need an instance of DATEV Rechnungswesen with the subscriptions to the relevant services for your use case to run your integration in production.
  • Talk to us for advice on how to achieve this in a fast and cost-effective way!
However, creating journal entries, as well as performing a range of other operations, can also be done through DATEV Unternehmen Online. In these cases, Unternehmen Online acts as an intermediary between the client (you) and DATEV Rechnungswesen. Typically, data is uploaded to Unternehmen Online and the tax advisor can approve and amend the data, before submitting it to DATEV Rechnungswesen. This can be achieved through the “Belege bereitstellen”-feature in the Unternehmen Online UI. However, as already mentioned, journal entries, customers and suppliers can be submitted directly to Rechnungswesen through this interface.

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Authenticate with the long access token

Provide your customer the long access token procedure to authenticate to DATEV Rechnungswesen. The token is valid for 2 years and can be used for authentication throughout that period to the API. There are two ways to retrieve a long access token:

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🔁 Option 1: Interactive Authentication Flow

1

Authenticate to DATEV Rechnungswesen

  • Log in to datev-rewe-longtoken using the /auth endpoint. Make sure to include the query parameter environmentSelection=true in the request.
2

Choose your Company

  • From the list, select the target company for your API usage.
  • The selected company’s ID is stored automatically — you do not need to send it in subsequent requests.
3

Retrieve the long token

  • Click “submit”.
  • Accept the connection to your application to complete the process and retrieve your token.

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⚙️ Option 2: Manual Token Retrieval

1

Authenticate to DATEV Rechnungswesen using the short token

  • Log in to datev-rewe using the /auth endpoint.
  • Retrieve the Account key from the authentication response.
2

GET company ID

  • Fetch the company list using the Get Companies endpoint.
  • From the list, select the target company to use for the API calls.
3

Authenticate to DATEV Unternehmen Online using the long token

  • Authenticate again using the /auth endpoint, but this time with datev-rewe-longtoken target system, providing the chosen companyId as input.
  • Complete the authentication process.
Warning: The long token is only valid for API calls that include the specified company in the input.

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Pilot

TARGET_SYSTEM: datev-rewe-trial It is possible to get access to a pilot phase for DATEV Rechnungswesen through Maesn. The pilot allows you to connect via our Unified API to retrieve data directly from DATEV Rechnungswesen, such as financial records and account ledgers.
  • Get in touch with your contact person at Maesn to join the pilot and unlock early access.
If you are not sure who your technical contact is, do not hesitate to reach out to us.