If they’re using fake papers to work, they’re paying income tax (and payroll tax is paid for them as well) but can’t file for a refund or unemployment insurance payments. They pay into Social Security but won’t be able to collect it (though I think anyone under 50 can probably relate to that).

When they buy things, they pay sales tax like anyone else.

They pay their landlady’s property tax if renting and pay it themselves if not.