Individual Taxpayer Identification Number
The Internal Revenue Service or the Social Security Administration issues all citizens an Individual Taxpayer Identification Number, or ITIN. For most employees and sole proprietorships, the ITIN is the Social Security number. If your status changes -- from a sole proprietorship to a partnership or corporation, for example -- the IRS issues a new Federal Employer Identification number, or FEIN. You are required to report this change on an updated W-9 form.
A change in your citizenship status is rare, but if it does change, you must file a new W-9 form. If you are currently a U.S. citizen, this status normally changes only if you leave the country permanently, have your citizenship revoked or voluntarily renounce your status. If your status changes, send a new W-9 form immediately, as your employer may need to change his records. The taxation process for non-U.S. citizens working in the United States often differs from the process for a citizen.
Backup Withholding Status
The most common change to a taxpayer's status is whether or not the person is subject to backup tax withholding. You are subjected to this type of withholding if you omitted or lied about information, such as your ITIN, on your previous W-9 form, if you did not certify that you are exempt from withholding or if you underreported your interest or dividends and did not tell your employer to withhold funds.
The IRS alerts you if you are subject to backup tax withholding and gives the reason for this. The agency also alerts you when you are no longer subject to withholding. If you are subject to backup withholding, you must change your W-9 to reflect this; you must also change it if you become exempt.
It is not your employer's responsibility to ask you if anything has changed on your W-9 form. If your taxpayer number, Social Security number, citizenship status or tax-withholding exemption status has changed in the past year, you must contact your employer and request a new form. If you think you may have unusual circumstances that will affect your W-9 and may require you to update it, contact your employer first and ask. The human-resources department at your place of employment should be able to answer your question; otherwise, contact the IRS.