No, you do not need any additional accounting software if you are a customer of No, as a customer of Kontist Tax Service, you do not need any additional accounting software. Instead, you can simply create your invoices and upload your receipts with Kontist. Kontist Steuerberatung is also using the accounting software provided by Kontist GmbH to book your transactions.
If you have been using an accounting tool in the past, you have a legal obligation to keep the receipts for 10 years, so you should make a data export before you cancel other tools.