What if employer didn't take any federal taxes out of my paycheck, when they were supposed to

[rjs]

Are you an employee (you get a W-2) or are you an independent contractor (you get a 1099-NEC)? If you are an independent contractor they are not supposed to take any tax out of your pay.

If you are an employee and no tax was withheld, it's too late to do anything about it now for 2023. You will have to pay the tax that you owe when you file your tax return. But if your income is low, it's possible that you do not have to pay any federal income tax. In that case, the employer was correct to not take any tax out of your pay.

For 2024 you can use the Tax Withholding Estimator on the IRS web site to figure out what to put on the W-4 form that you give to your employer, and give them a new W-4 if necessary.

[Mike9241]

are you sure they are treating you as an employee where you'll get or got a W-2? if you get a 1099-NEC they're treating you as an independent contractor making you responsible for paying any federal or state taxes. 

If you are concerned that your employer is improperly withholding or failing to withhold federal income and employment taxes you should report your employer by contacting the IRS at 1-800-829-1040. Keep in mind, however, that whenever you start a new job, you're supposed to fill out Form W-4 which is used to figure withholding.