I understand how challenging it is when you encounter error messages when filling out your W-2s in QuickBooks Desktop (QBDT), SelinaLieu.  I'll outline some troubleshooting steps to ensure you can continue your W-2 filing.

The "incorrect file extension" error typically means your state portal doesn’t support the file format, even if you're using the correct ".TXT" extension. Since you’ve confirmed that you're using the right format, we can update your tax table to ensure compliance with federal and state regulations, minimizing potential filing errors.

Here's how:

1. Go to the Employees tab and select Get Payroll Updates.
   
2. To identify if the number next to 'You are using tax table version' is the correct version, check the latest payroll news and updates.
3. To find more details on your tax table version, select Payroll Update Info.
4. To get the latest tax table, select Download Entire Payroll Update. Then click Update.
   

If you encounter errors when updating the Payroll Tax table, check this article for detailed guidance: Get the latest tax table update in QuickBooks Desktop Payroll.

I also recommend updating QuickBooks Desktop to the latest version to access critical fixes, and enhanced features, and optimize overall system performance. For more information, visit this article: Update QuickBooks Desktop to the latest release.

Lastly, make sure your W-2 file is saved with the ".TXT" extension. Sometimes just renaming a file doesn’t actually change its format.

However, if you’re still having issues after following these steps, I recommend reaching out to our Live support team.

Additionally, here are some resources you can check out as a guide to managing your W-2 forms in QuickBooks Desktop:

• Fix an incorrect W-2 and W-3
• Print your W-2 and W-3 forms

Your experience is important to us, so please don't hesitate to drop by again in this thread if you need additional assistance when filling W-2s in QBDT.