I am getting income support benefit from
government, is it haram if do not tell them that i am getting an other source of money?
If it is a condition of their giving you assistance that they should be told of other sources of income or how much you are getting, then it is not permissible for you to hide that from them. Similarly, if it is known that they only help those who are in need and you are not in need, then it is not permissible to take this assistance. And Allaah knows best.