My next payroll is for 12/15/2023 to 12/29/2023 payable january 4, 2024.....is this 1st quarter 2024, or 4th quater 2023?

Let me share some insights about pay periods, sierra. 

The mentioned paycheck dates fall under the first quarter of 2024. Thus, in the first quarter of 2024, you will pay the taxes for pay periods dated 12/15/2023 to 12/29/2023. 

Additionally, check out this article to learn how to create, manage, assign, or update pay schedules: Set up and manage payroll schedules. 

Comment below if you require further assistance with payroll-related concerns. Keep safe!