If your employee is an exempt salaried employee, under the Fair Labor Standards Act, you aren't required to pay overtime for extra hours.
You can determine if your employees are exempt from the FLSA overtime rules by looking at 2 key things:
If your employee doesn't pass the test for exempt status, you're required by federal law to pay overtime hours for any time worked in excess of 40 hours a week. For example, if your non-exempt employee works 45 hours per week, they would be entitled to 5 hours paid at time and a half, not including any additional hours worked beyond 45.
Some states have laws that extend the rights under the Fair Labor Standards Act, and these can oftentimes be more rigorous than federal laws.
For example, New York extends overtime to some occupations that are considered exempt under the FLSA, regardless of the amount of their regular pay rate.
For other states, this list can be a helpful guide.
On November 22, 2016, a federal court put a hold on the Department of Labor's increase to the minimum salary requirement for the Executive, Administrative, and Professional exemption under the Fair Labor Standards Act, which was scheduled to take effect on December 1, 2016. This is currently pending legal action.
Ultimately, the Fair Labor Standards Act doesn't trump state laws, and employees are subject to whichever law, state or federal, provides the highest pay for overtime. Be sure to check with your specific state laws to ensure full compliance.