QB migrated file to Online, only 9 of the 18 employees were there, 2 were vendors, changed their info, worked fine. 1 had error wrong SS number, which is correct. Fix?

Hi there, lblackett. Thanks for bringing this up on the QuickBooks Community page.

The issue may steam when migrating your files from QuickBooks Desktop to QuickBooks Online. 

Before we proceed with the troubleshooting steps, can you help me verify whether these employees are set up as employees or vendors (track payments for 1099) in QuickBooks Desktop? This way, I can provide you with the appropriate steps to address the issue. Any additional info would be much appreciated.

Since you're unable to add them, I suggest reimporting your QB files again to QBO. Doing this will replace your incorrect imported data and possibly fix the error.

If you're still getting the same results, I'd suggest deleting your imported employees or inactivating vendors.

Here's how to delete an employee's profile in QBO:

1. Go to Payroll, then Employees.
2. Select your employee. 
3. Under the Actions drop-down list, click Delete employee.
4. Select Delete employee. 

Please note that you can only delete an employee if you haven't created any paychecks on them in QuickBooks Online Payroll. If you can't delete them, change their status instead. For employees with incorrect info, you can edit their profile instead.

If these are vendors, follow these steps to make them inactive: 

1. Go to Expenses and click Vendors.
2. Select Make inactive in the drop-down menu beside the vendor you want to make inactive.

Once done, you can add vendors with the correct info and SSN to QuickBooks.

To learn more about the steps you should take after you move from QBDT to QBO, check out this guide: What to do after you move from QuickBooks Desktop to QuickBooks Online.

If you have further questions about migrating your files, just add them to the thread. I'll be here to help you out. Have a good one.