Box D, the
control number is not required to file your return, you can 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