The W-4 form is four pages of instructions and worksheets, not just the front page with the signature that you might turn into the employer. If a person’s only income is a part-time job, and they expect make less than $12,000 per year, or less than $24,000 per year if married and it is the only job in the family, then they would not have federal Federal income tax withheld. However, if a married couple has more than one job in between them, or a single person has more than one job, it is important to use all the instructions and worksheets on the W-4 form, or to use the online tool that is linked there, to determine how to set up each W-4 for each job so that the withholding is correct. Otherwise, you could have two little tax withheld and owe additional tax at the end of the year.
