If you issue a W-2 then you will need a EIN.
You should read IRS Pub 926 (Household Employer's Tax Guide) for a lot of information about withholding and W-2's
https://www.irs.gov/pub/irs-pdf/p926.pdfAlso Pub 15 for withholding tables and other information for employers.
https://www.irs.gov/pub/irs-pdf/p15.pdf
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
