It will be determined by the particular legislation, but the most talked about one in the United States started being applied in 2025. The rule took effect on wages earned starting January 1 of the year although it was passed earlier in the year. This timing is so effective as to allow the payroll systems and employers to work out the correct calculations. Employees experience the impact on their paychecks when overtime hours become subject to the definition of the law- which is usually the number of hours worked after 40 hours in a week which is paid to potential workers. This rule is restricted to federal income tax, but not to the state income tax unless the state has a similar policy. When Does No Tax On Overtime Start