While filling out form 4852, the section for EIN (Employer Identification Number) only needs to be completed if it is known. If you don't have it you can leave this blank.
For more information regarding Form 4852, Substitute W2 please visit the FAQ and the IRS link below:
https://www.irs.gov/uac/about-form-4852
https://ttlc.intuit.com/replies/5451995
