Which provincial/territorial tax rate will be used to calculate tax withholdings on an employee's income if that employee does not work from the employer's place of business?

1-The tax rate of the employee's province/territory of residence while employed

2-The tax rate applicable to the province/territory the employee works from most often

3-The tax rate applicable to the province/territory from which the employer generates the pay

4-The tax rate of the employee's province/territory of residence on the last day of the taxation year