Could you please be more clear on your question?
I’m assuming you are referring to the Employer Identification Number (EIN). If I’m correct, you can find it in Box b of your W-2.
In case your return was rejected because of an EIN mismatch, double check the numbers that you entered and make sure there are no spaces or special characters.
To see more detailed information where to find it, open the link below:
How do I find my employer's EIN or Tax ID?
If I'm wrong, and you are talking about something else, please respond in this forum to what you mean with EIB.