From the Hotline: Correcting a Medical Contribution Withholding Error
Question: How can a California company correct an employee medical contribution withholding error?
Answer: In general, an employer may only deduct from wages amounts authorized by the employee, as per California labor code.
You can certainly work with the affected employee(s) to recover amounts over a period of time to correct the matter. Best practice is to come up with a written and signed agreement to increase payroll deductions to recover missed premiums over a stated period of time (a specified number of pay periods, for example) to recover the amount due and to lessen the burden to the employee.