I work in immigration law and it seems a lot of pe ow have the same question of how undocumented immigrants pay taxes. If you don't have a social security number you can ask the IRS for what is called an ITIN and you can file with that number instead. Undocumented immigrants pay taxes for two main reasons. First, if they ever appear before an immigration judge, they can show that they are contributing to society. Second, undocumented workers just want work and they want to be a part of the community and paying taxes allows them to feel as though they are capable of supporting their family and are capable of being a citizen one day.