Why I can not e-file it showed that because control number on W-2 is only one digit . But I checked today with employeer and it is not a mistake it is only one digit

[DawnC]

You can leave that box blank; don't enter anything and it will work for e-filing.  

It does not matter what is in that control number box.  If there is a problem, it only prevents you from importing the W-2.  Since you can't import it, you will need to manually enter it.  You won't have an issue when you get to the filing step because of the control number.  

[Taxfile]

Said the same to me so I just deleted that box and was able to file

[KrisD15]

JUST LEAVE THAT BOX BLANK.

The control number is used by the accounting department of the company you work for. The IRS does not use it. It is not required. It is on the W-2 in TurboTax to match what your W-2 might look like, but it does not calculate into anything. 

@biljap72