The IRS generally publishes information on its website about changes in the tax law. Also, IRS Publication 553, “Highlights of (Year) Tax Changes” will provide you with information on the tax changes from one year to the next. This publication can be downloaded from the IRS website. You should review the principal changes in the tax laws to see how they affect your taxable income, adjustments, deductions, and credits. Certain credits or deductions may expire, and new credits and deductions may go into effect.
You can also look at the amounts that generally change from year to year, such as the amount of the personal and dependent exemptions, the standard deduction, and the limits or phase-out amounts that apply on certain deductions or credits to see how they may affect your tax liability.
How To Adjust Your Withholding
You adjust your withholding by giving your employer a new Form W-4. You can change the amount that is being withheld by changing any of the information you reported on the W-4 you originally gave your employer, that is, the filing status, number of withholding allowances, or the additional amount to be withheld. You should give your employer a new Form W-4 as soon as possible whenever you experience a significant event that changes your income tax status, and whenever you become aware that the information you included on the Form W-4 you originally submitted no longer applies. You can submit a new W-4 at any time you wish, and for any reason, to change your filing status, change the number of withholding allowances, or request an additional amount to be withheld that is more or less than what you originally submitted.
Increasing Your Withholding
You can increase your withholding by either decreasing the number of withholding allowances you are claiming on line 5 of Form W-4, or by indicating an additional amount to be withheld on line 6, or increasing that amount if you had previously indicated an additional amount to be withheld.
You can calculate the additional amount to be withheld by completing Worksheet 1, Projected Tax, and Worksheet 2, Projected Withholding, in IRS Publication 919. If you change the additional amount to be withheld based on the calculations from these worksheets, you would not change the number of withholding allowances on your Form W-4. You would leave this number the same as it was on the last W-4 you gave your employer, and would change only the additional amount to be withheld.