You are entitled to receive the benefits you paid into while working as a public employee in California. However, if you are collecting both Social Security and California Public Employees Retirement System benefits, your Social Security benefits may be reduced depending on your individual circumstances.
You can collect both your Social Security and CalPERS benefits if you paid into both systems while working. Typically, your monthly paycheck was reduced by $133.33, representing the amount your employer deducted for CalPERS. Money deducted under the category of FICA went toward Social Security.
If money was deducted for CalPERS from your wages, but deductions were not always made to Social Security from these same wages, your Social Security benefits may be reduced. This is known as the Windfall Elimination Provision. For example, the wages of certain county employees are subject to CalPERS deductions, but not Social Security deductions. As a result, when the employee collects their retirement benefits from both Social Security and CalPERS, the Social Security Administration will reduce a portion of the payment to prevent overpayment, i.e. windfall, of Social Security benefits.
Your Social Security benefits may also be reduced if you're also entitled to receive a portion of your spouse's Social Security payments. This can also apply to Social Security benefits you may be entitled to receive after your spouse dies. Typically, SSA reduces the amount of Social Security benefits by the amount of your CalPERS benefits. This reduction is known as the Government Pension Offset.
Just because the SSA reduced your benefits doesn't mean it wasn't done in error. It is not uncommon for SSA officials to reduce the Social Security benefits of government employees receiving CalPERS benefits by mistake because of a misunderstanding of pension rules. Take your paperwork to your enrollment benefits administrator to review if you have concerns.