السلام عليكم ورحمة الله وبركاته Some people in my country where I live in the west collect cash so they could avoid paying taxes to the government. Is this allowed for someone to do. If not how should we advise someone who is doing this. Also what do they do with the money that they earned

They have to be truthful and do what is upon them to these lands or they leave these lands. If the land allows u and says collect cash so that u don't pay taxes then it is allowed. But if they are doing this to run away from paying taxes and the land tells u whether u get cash or in the bank u should pay a percentage in taxes then it is haram. This is what sh Muhammad Hisham has explained to me.