You cannot change your W-4 retroactively. The number of allowances is used to determine the amount of federal tax to be withheld from your paychecks. If you overstated your allowances, you may have too little tax withheld and may have some tax due (and possibly a penalty for under-withholding).
To change your allowances, you need to submit as soon as possible a new W-4 form to your employer.
Please this TurboTax article:
https://turbotax.intuit.com/tax-tips/irs-tax-forms/what-is-a-w-4-form/L2NapDzX2
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
