This thread is talking about Box d (d) on a W-2 which might report a control number.
A control number is not needed by tax Software, and not needed by the IRS.
If you mean EIN Number, that is in Box B (b) which is located on the W-2 ABOVE the name of the employer.
If you are asking about something else, continue with this question or start a new question
NOT THIS, THIS IS NOT NEEDED
EIN on W-2 IS NEEDED