To be clear, the amount of tax that is withheld from your pay is determined by the W-4 form that you fill out and give to your employer. If too little tax is being withheld, it's because you did not fill out the W-4 correctly. You have to give your employer a new W-4 that you adjust to have more tax withheld. You can use the Tax Withholding Estimator on the IRS web site to figure out what to put on your W-4 form. It will show you how to adjust your withholding to get the approximate refund amount that you want.
