Hello there, @ccarrllc.

Let me share information on setting up your 401(k) catch up contribution on your employee here in QuickBooks Online (QBO).

You can only choose one deduction from your 401(k) contribution to set up a retirement plan for your employees in QuickBooks. This may be the reason why you receive an error message if you are trying to add a catchup contribution when you set up your 401(k) account.

In order to create a catch up distribution plan, the regular retirement item must be deleted from your employee's. This does not delete the year-to-date amount of the item payroll. It will remove the deducted item, then apply the balance to the new catchup distribution plan.

Let me guide you on how:

1. Choose the Payroll on the left panel.
2. Select Employees, then choose which employee.
3. At the Deductions & Contributions table, click Edit.
4. Click the Trash bin icon on the 401(k) deduction you want to remove.
   
   

Once you’re done, you can now add the 401(k) Catch-up retirement plan. Given that you’re still on your Deduction & Contribution page of your specific employee, you can follow the steps below:

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

You can check this article for further information regarding the steps that I have mentioned above: Set up or change a retirement plan.

Moreover, I’ll be leaving you this articles that tackles on creating, managing, assigning or updating your employee’s pay schedules in QBO: Set up and manage payroll schedules.

Let me know if you have other inquiries with setting up the deductions and contributions with your employees here on QBO. I’m just a post away.