The control number I have is 3 and it is telling me that it is invalid. What do I need to do?

[ToddL]

If your W-2 doesn't have a box d (or the program believes it is invalid) , it's no big deal – you can leave it blank or enter a "dummy" control number.

How to do that?

I have no Box D or Control Number on my W-2

(You may have to delete the Form W-2 and re-enter it in the W-2 interview).

See: How do I delete forms in TurboTax Online?

After deleting the W-2, log out of the program. When you log back in, use the Delete a Form tool to see if the W-2 has been removed from the list of forms in your return.  If it is gone, you should be able to re-enter it in the W-2 interview and complete your return.