On the main menu select Application Settings and then Global Settings (Commission and Decimal Places).

A new screen appears where you can set your Commission Level as well as Decimal Places.

There is also an option to use Betting Tax instead of Commission. This is calculated differently to Commission. Betting Tax has been added after German users are forced to pay 5% Betting Tax. Bookmakers usually only charge this tax on winning bets and when they do it is based on your entire bet winnings. This includes your stake.

Commission is for Exchanges such as Betfair and Betdaq. Commission is based on your profit only.