How do i change the 401k deferment amount for over 50 years old employee so they can max out their contribution amount

Welcome to the Community, @slrmahj. I'm here to help you change your employee's 401k deferment in QuickBooks Online (QBO).

In order to maximize your employees' contributions, we need to create a catch-up distribution plan. To do this, we'll have to delete the regular retirement plan from your employee's profile. Don't worry, this won't delete the year-to-date amount of the item payroll. It will simply remove the deducted item and apply the balance to the new catch-up distribution plan. 

Let's delete the existing plan:

1. Go to Payroll, then select Employees.
2. Double-click your employee to open. In the Profile page, navigate to Deductions & contributions.
3. Click Edit, then click the Trash bin icon beside the existing 401(k).

Remain on the same page. After deleting the 401(k) plan, lets now create the 401(k) Catch-up plan:

1. Click the + Add deduction/contribution.
2. Select Retirement plans in the Deduction/contribution type dropdown.
3. Choose 401(k) Catch-up in the Type dropdown.
4. Fill in the necessary details, then click Save.

For further information on these steps, please refer to this article: Set up or change a retirement plan.

Additionally, I'd like to share an article on creating, managing, assigning, or updating your employee's pay schedules in QBO: Set up and manage payroll schedules.

Feel free to ask if you have any other inquiries about setting up deductions and contributions for your employees in QBO. I'm here to help you out.