By following the indications for each line on this worksheet, you should come up with a total number of withholding allowances that will be appropriate for your tax status. By claiming this number of allowances, your tax withholding for the year should closely match your actual tax liability. This is the purpose of the worksheet. As indicated in the notes at the bottom of this worksheet, if you expect to be able to itemize deductions or expect to have adjustments that will reduce your taxable income, you may be able to reduce your tax withholding, and should complete the Deductions and Adjustments Worksheet. And, if you have more than one job, or you are married and both you and your spouse work, you may need to have more tax withheld. You should complete the Two-Earner/Two-Job Worksheet in that case.
You should claim one allowance for yourself on line A unless someone else can claim you as a dependent. Add an additional withholding allowance on line B if one of the conditions indicated there applies in your case. This is not the same as, and should not be confused with the exemption you claim for yourself on line A, or the exemption you claim for your spouse on line C. Rather, it is an additional allowance to be taken into account in determining the amount of tax to be withheld from your pay. In this sense, the allowances for purposes of completing Form W-4 and having tax withheld from your pay, are not the same as the exemptions you claim when you file your annual income tax return.
On line C you can claim an allowance for your spouse’s exemption. You would generally claim this allowance if you are planning to file jointly and your spouse, if he or she is working, is not claiming an allowance. You can both claim your own allowances even though you intend to file jointly. If you are married and intend to file separately, both spouses should claim allowances for their own exemptions.