You may have an additional amount withheld from your earnings (paycheck) by asking your employer to update the information on your Form W-4.
- Enter the amounts that apply to you in lines A-H and enter the total allowances in Line 5 of the lower section of form W4. The allowances you declare affect your withholding according to your pay. Neither you or your employer can manipulate how much is withheld based on the Allowances you declare(read this section carefully as this provides the exemptions that you are allowed to take)
- If you already know the additional amount withheld from you pay you can enter this amount in Line 6 of Form W4. This amount is totally under your control.
For you convenience I have provided a link to Form W-4 from the IRS webpage.