Immigration helps finance Social Security by expanding the labor force and increasing payroll tax revenue, which largely funds the program. A recently introduced congressional bill would reduce lawful permanent immigration by about 50 percent. This brief shows that this bill, if enacted, would worsen the already strained finances of the Social Security trust funds. Program revenues would fall faster than expenditures, raising the present value of Social Security’s unfunded future obligations by $1.5 trillion, or 13 percent, over the next 75 years. Restricting immigration would require additional Social Security benefit cuts or tax increases to balance the system.