In Box D, the control number, you may not have anything in that box, if that is the case, just leave it blank.  If you are trying to import your W2 and don't have anything in Box D and if its required for import, you will have to manually enter your W2 instead.

See below for more information about how to enter a control number in TurboTax.

https://ttlc.intuit.com/replies/4417180