Their employers pay taxes on their wages through their fake ss numbers. They pay sales tax when they buy things from the store

https://www.irs.gov/individuals/individual-taxpayer-identification-number

An Individual Taxpayer Identification Number (ITIN) is a tax processing number issued by the Internal Revenue Service. The IRS issues ITINs to individuals who are required to have a U.S. taxpayer identification number but who do not have, and are not eligible to obtain, a Social Security number (SSN) from the Social Security Administration (SSA).

Perhaps not income taxes, but maybe taxes on goods and services, property taxes, etc? Can’t say for certain though.