Undocumented immigrants can't file income tax, because they are undocumented. However, they also can't utilize the majority of our costly social services, because they, obviously, don't have documentation. They can't sign up for welfare programs, utilize police resources for fear of being deported, etc.

Overall though, they are also human. They produce similar economic demand to Americans. They pay sales tax. Their landlord pays tax on their rent. They are also often paid less than Americans because they have no ability to enforce the law through legal means (again, for fear of being deported), but still have to buy things like food, which is taxed.

Thus, they tend to, at a bare minimum, take roughly about what they put in, leaving a mostly neutral effect on the economy.

Immigration is generally regarded to boost innovation overall, lead to higher education rates within the workforce, and creates higher overall economic productivity., which is an effect on the economy that isn't just taxes in, taxes out.

Of course, the best option we have is to grant them amnesty, because that then means they can file & pay income taxes, can more easily be statistically measured and analyzed as a group, and can engage in class solidarity through union organization, which raises working conditions and wages for all workers.