Circular E

Circular E is the IRS publication which tells employers how much income tax to withhold from their employee’s paychecks.

Circular E tells how to calculate tax for people with different filing statuses such as married filing joint, married filing separately, head of household, or single. It shows how much to withhold if workers are paid on time schedules such as daily, weekly, biweekly, semimonthly, or yearly. It explains how to include the number of exemptions in your calculations. Circular E is very useful for any employer who is calculating tax withholding without a computer.

https://accounting.uworld.com/cpa-review/lc/accounting-dictionary/term/circular-e/