EIN stands for "Employer Identification Number".  The IRS uses an EIN to keep track of the taxes you owe and pay as an employer, much like it uses your Social Security number to keep track of your individual (personal) taxes.  If you do not have an EIN, get IRS Form SS-4, Application for Employer Identification Number.

You may enter "Applied For" in the NannyPay software Set Up Screen if you don't have an EIN number by the time you start using NannyPay.  See Setting Up NannyPay Software for more information.