The amount of income tax your employer withholds from your regular pay depends on two things.

Form W-4 includes three types of information that your employer will use to figure your withholding.

When you start a new job, you must fill out Form W-4 and give it to your employer. Your employer should have copies of the form. If you need to change the information later, you must fill out a new form.

If you work only part of the year (for example, you start working after the beginning of the year), too much tax may be withheld. You may be able to avoid overwithholding if your employer agrees to use the part-year method. See Part-Year Method in chapter 1 of Publication 505 for more information.

Events during the year may change your marital status or the exemptions, adjustments, deductions, or credits you expect to claim on your tax return. When this happens, you may need to give your employer a new Form W-4 to change your withholding status or number of allowances.

If the event changes your withholding status or the number of allowances you are claiming, you must give your employer a new Form W-4 within 10 days after either of the following.

Generally, you can submit a new Form W-4 whenever you wish to change the number of your withholding allowances for any other reason.

After you have given your employer a Form W-4, you can check to see whether the amount of tax withheld from your pay is too little or too much. See Publication 919, later. If too much or too little tax is being withheld, you should give your employer a new Form W-4 to change your withholding.

Form W-4 has worksheets to help you figure how many withholding allowances you can claim. The worksheets are for your own records. Do not give them to your employer.

In most situations, the tax withheld from your pay will be close to the tax you figure on your return if you follow these two rules.

But because the worksheets and withholding methods do not account for all possible situations, you may not be getting the right amount withheld. This is most likely to happen in the following situations.

To make sure you are getting the right amount of tax withheld, get Publication 919. It will help you compare the total tax to be withheld during the year with the tax you can expect to figure on your return. It also will help you determine how much additional withholding, if any, is needed each payday to avoid owing tax when you file your return. If you do not have enough tax withheld, you may have to pay estimated tax, as explained under Estimated Tax, later.

It may be helpful for you to know some of the withholding rules your employer must follow. These rules can affect how to fill out your Form W-4 and how to handle problems that may arise.

If you claim exemption from withholding, your employer will not withhold federal income tax from your wages. The exemption applies only to income tax, not to social security or Medicare tax.

You can claim exemption from withholding for 2009 only if both of the following situations apply.

Supplemental wages include bonuses, commissions, overtime pay, vacation allowances, certain sick pay, and expense allowances under certain plans. The payer can figure withholding on supplemental wages using the same method used for your regular wages. However, if these payments are identified separately from your regular wages, your employer or other payer of supplemental wages can withhold income tax from these wages at a flat rate.

You may have to pay a penalty of $500 if both of the following apply.

There is also a criminal penalty for willfully supplying false or fraudulent information on your Form W-4 or for willfully failing to supply information that would increase the amount withheld. The penalty upon conviction can be either a fine of up to $1,000 or imprisonment for up to 1 year, or both.

These penalties will apply if you deliberately and knowingly falsify your Form W-4 in an attempt to reduce or eliminate the proper withholding of taxes. A simple error or an honest mistake will not result in one of these penalties. For example, a person who has tried to figure the number of withholding allowances correctly, but claims seven when the proper number is six, will not be charged a W-4 penalty.

You do not have to make estimated tax payments until you have income on which you will owe the tax. If you have income subject to estimated tax during the first payment period, you must make your first payment by the due date for the first payment period. You can pay all your estimated tax at that time, or you can pay it in installments. If you choose to pay in installments, make your first payment by the due date for the first payment period. Make your remaining installment payments by the due dates for the later periods.

You do not have to pay estimated tax if your withholding in each payment period is at least as much as:

You also do not have to pay estimated tax if you will pay enough through withholding to keep the amount you owe with your return under $1,000.

If you show an overpayment of tax after completing your Form 1040 or Form 1040A for 2008, you can apply part or all of it to your estimated tax for 2009. On line 74 of Form 1040, or line 46 of Form 1040A, enter the amount you want credited to your estimated tax rather than refunded. The amount you have credited should be taken into account when figuring your estimated tax payments.

The credit will be applied to your payments in the order necessary to avoid the penalty for underpayment of estimated tax. You cannot have any of that amount refunded to you until the close of that tax year. You also cannot use that overpayment in any other way.

Each payment of estimated tax by check or money order must be accompanied by a payment voucher from Form 1040-ES. If you made estimated tax payments last year and did not use a paid preparer to file your return, you should receive a copy of the 2009 Form 1040-ES in the mail. It will contain payment vouchers preprinted with your name, address, and social security number. Using the preprinted vouchers will speed processing, reduce the chance of error, and help save processing costs.

Use the window envelopes that came with your Form 1040-ES package. If you use your own envelopes, make sure you mail your payment vouchers to the address shown in the Form 1040-ES instructions for the place where you live.

If you did not pay estimated tax last year, you will have to get Form 1040-ES (see inside back cover of this publication). Follow the instructions in the package to make sure you use the vouchers correctly.

If you file a joint return and you are making joint estimated tax payments, enter the names and social security numbers on the payment voucher in the same order as they will appear on the joint return.

If you want to make estimated payments by using EFTPS, by electronic funds withdrawal, or by credit card, see the Form 1040-ES instructions or How To Pay Estimated Tax in chapter 2 of Publication 505.

Your employer is required to provide or send Form W-2 to you no later than February 2, 2009. You should receive a separate Form W-2 from each employer you worked for.

If you stopped working before the end of the year, your employer could have given you your Form W-2 at any time after you stopped working. However, your employer must provide or send it to you by February 2, 2009.

If you ask for the form, your employer must send it to you within 30 days after receiving your written request or within 30 days after your final wage payment, whichever is later.

If you have not received your Form W-2 on time, you should ask your employer for it. If you do not receive it by February 15, call the IRS.

Form W-2 shows your total pay and other compensation and the income tax, social security tax, and Medicare tax that was withheld during the year. Include the federal income tax withheld (as shown on Form W-2) on:

In addition, Form W-2 is used to report any taxable sick pay you received and any income tax withheld from your sick pay.

If you had gambling winnings in 2008, the payer may have withheld income tax. If tax was withheld, the payer will give you a Form W-2G showing the amount you won and the amount of tax withheld.

Report the amounts you won on line 21 of Form 1040. Take credit for the tax withheld on line 62 of Form 1040. If you had gambling winnings, you must use Form 1040; you cannot use Form 1040A or Form 1040EZ.

Most forms in the 1099 series are not filed with your return. In general, you should be sent these forms by February 2, 2009. Unless instructed to file any of these forms with your return, keep them for your records. There are several different forms in this series, including:

If you received the types of income reported on some forms in the 1099 series, you may not be able to use Form 1040A or Form 1040EZ. See the instructions to these forms for details.

If you receive a form with incorrect information on it, you should ask the payer for a corrected form. Call the telephone number or write to the address given for the payer on the form. The corrected Form W-2G or Form 1099 you receive will have an “X” in the “CORRECTED” box at the top of the form. A special form, Form W-2c, Corrected Wage and Tax Statement, is used to correct a Form W-2.

If you file your return and you later receive a form for income that you did not include on your return, you should report the income and take credit for any income tax withheld by filing Form 1040X, Amended U.S. Individual Income Tax Return.

If you are married but file a separate return, you can take credit only for the tax withheld from your own income. Do not include any amount withheld from your spouse's income. However, different rules may apply if you live in a community property state.

Community property states are listed in chapter 2. For more information on these rules, and some exceptions, see Publication 555, Community Property.

If you file your tax return on the basis of a fiscal year (a 12-month period ending on the last day of any month except December), you must follow special rules to determine your credit for federal income tax withholding. For a discussion of how to take credit for withholding on a fiscal year return, see Fiscal Years (FY) in chapter 3 of Publication 505.

If you and your spouse made separate estimated tax payments for 2008 and you file separate returns, you can take credit only for your own payments.

If you made joint estimated tax payments, you must decide how to divide the payments between your returns. One of you can claim all of the estimated tax paid and the other none, or you can divide it in any other way you agree on. If you cannot agree, you must divide the payments in proportion to each spouse's individual tax as shown on your separate returns for 2008.

If you made joint estimated tax payments for 2008, and you were divorced during the year, either you or your former spouse can claim all of the joint payments, or you each can claim part of them. If you cannot agree on how to divide the payments, you must divide them in proportion to each spouse's individual tax as shown on your separate returns for 2008.

If you claim any of the joint payments on your tax return, enter your former spouse's social security number (SSN) in the space provided on the front of Form 1040 or Form 1040A. If you divorced and remarried in 2008, enter your present spouse's SSN in that space and write your former spouse's SSN, followed by “DIV,” to the left of Form 1040, line 63, or Form 1040A, line 39.