Which of the following options is essential in correcting a tax withholding error?

Adjusting future withholdings is the correct approach to correcting a tax withholding error because it directly addresses the issue at hand: ensuring that the correct amount is withheld from an employee's paychecks moving forward. By recalculating and updating the withholding amounts, the employer can prevent further discrepancies and help the employee avoidUnderpayment or overpayment of taxes, which could lead to penalties or issues during tax filing.

Taking this action not only rectifies the immediate error but also aligns future paychecks with the correct withholding requirements. Accurate withholding is crucial for both compliance with tax regulations and for maintaining the employee's financial planning.

The other options do not adequately resolve the core issue of withholding errors. Filing a lawsuit would be inappropriate for this context as it does not offer a solution to the payroll issue; it's a legal remedy that would be used in significantly different circumstances. Counting the error as a loss does not address the underlying mistake and could result in ongoing complications. Allowing the employee to handle it places the burden on the employee instead of the employer, which can lead to further confusion and potential legal issues, as the employer is responsible for correct payroll practices.