It would be good when negative expense amounts would be allowed. This way it's easy to add credited expenses. At the moment you can only add positive amounts and it's really difficult to add a credit expense. This would be an easy feature to add as it would only be needed change the settings for the amount field to also allow for for a negative amount to be filled in. Or just add a an option just like tax inclusive or exclusive, which is positive by standard but can also be set to negative.