What should an employee do if federal withholding is zero?

First review the payroll inputs before assuming the result is right or wrong.

Check the employee's current Form W-4, filing status, multiple-job entries, credits, additional withholding, pay frequency, taxable wages after pre-tax deductions, and whether payroll is treating the worker as an employee.

If the withholding is too low, the employee may submit a corrected Form W-4 or make estimated tax payments to reduce a year-end balance. That protects the employee's own tax position. It does not excuse an employer from applying payroll rules correctly.

If the employer is treating the worker as a contractor instead of an employee, the issue may become a worker-classification question.