ERRORNo "NY Metropolitan Commuter Transportation Mobility Tax" Rate has been defined on date (employee's name). You must complete your state and/or employee tax setup

Good day, smartherapypc.

It's possible that a tax rate or effective date is not added for the NY Metropolitan Commuter Transportation Mobility Tax in QBO. This is a tax imposed on certain employers and self-employed individuals engaging in business within the metropolitan commuter transportation district (MCTD).

I'll share with you the steps on how to complete the local tax setup in the employee's profile. Here's how:

1. Go to the Payroll menu and proceed to the Employees tab.
2. Click the name of the employee that's mentioned in the error message.
3. Look for Tax withholding and click Edit. 
4. Scroll-down to the Local Taxes section and review if the New York Mctmt Er, New York County box is checked.  If the employee is not subject to this tax, uncheck the box and click Save. 

If the employee is taxable to this item, keep it checked and proceed to the Payroll Settings section. Then, finish the setup by following these steps:

1. Go to the Gear icon and select Payroll Settings.
2. Look for New York Tax and click the pencil icon beside it. 
3. Locate NY Metropolitan Commuter Transportation Mobility Tax Rates, then click the Change or add new rate link.
4. Put in an effective date as well in the Effective date field.
5. Click OK and select Done. 

That should remove the error when trying to create paychecks. Feel free to check out this link and article for additional details and references as well:

• https://www.tax.ny.gov/bus/mctmt/
• Set Up Local Taxes in QuickBooks Online Payroll

Let me know if you're able to run the payroll successfully. You can also post additional questions if you need anything else.