The standard tax deductible rates are preset for each tax year.
You can change this default rate in-app Menu > Settings > Rates by using the Custom Business Rate field. This feature is very useful if your company reimburses you at a different rate.
You can also add your own custom Purpose and specify a different rate than the default. This feature is useful if you want to log trips and generate reports for separate companies, projects, etc. Go to in-app Menu > Settings > Purposes to set up your custom purposes for deducting trips.
To classify trips using a custom Purpose, tap the bottom-center grey icon on your trip card.