Payroll taxes withheld from employees' wages and salaries are liabilities of the employer. The payroll taxes withheld from employees include the employees' portion of the FICA or Social Security and Medicare taxes, federal income taxes, and state income taxes. The amounts withheld are really the employees' money that the employer is required by law to withhold and remit to the government. In other words, the employer is acting as an agent by withholding and remitting the employees' money. These taxes are not expenses of the company withholding them. They are a liability until the money is remitted to the government.
Payroll taxes which are not withheld from employees are expenses of the employer. Two examples of payroll taxes that are not withheld from employees but which must be remitted to the government by the employer are the employer's portion of the FICA or Social Security and Medicare taxes and the state and federal unemployment taxes. Since these are to be paid by the employer, these are expenses. They are also liabilities until the employer remits the required amounts to the government.