IRS Publication 15

IRS publication 15 is a federal guidebook for people preparing payroll taxes.

IRS Publication 15 includes the tables for figuring federal payroll withholding tax on employees. It also includes information on related topics such as who is a legal employee, applying for an Employee Identification number, how to deposit tax in a timely manner, using third party payroll companies, computing the earned income credit, computing social security taxes, computing federal unemployment taxes and filling out federal form 941. It does not include information on computing state income taxes.

https://accounting.uworld.com/cpa-review/lc/accounting-dictionary/term/irs-publication-15/