Most agencies dealing with large volumes of people require a quick and easy way to differentiate one individual from another.

Without relying on names that can and, (as anyone who’s received an early-morning collections call for a credit card held by someone with a similar name who lives on the other side of the continent, often are) shared by several people. The simplest way is to assign each individual a number. We’re well used to this phenomenon – we have license plate numbers, bank account numbers, health card numbers.

Revenue agencies are no different. The IRS in particular deals with millions of people. US citizens are eligible for a Social Security Number, or SSN, which, amongst other functions, identifies them to the IRS when it comes time to file their taxes.

But what about non-US citizens? Canadians and other non-US citizens are rarely eligible for an American SSN, but may be required to file US taxes for a number of reasons, ranging from working in the United States, to receiving US royalties on a piece of intellectual property, to wanting to recover money lost in gambling withholding taxes after a vacation in Las Vegas.

Enter the Individual Taxpayer Identification Number, or ITIN. Unlike an SSN, an ITIN is used only for US Federal tax purposes. It isn’t valid as identification in any circumstances unrelated to the Federal tax system, confers no benefits, and has no bearing on any immigration procedures you might have underway. Obtaining an ITIN will, however, allow you to file a US tax return, and receive any applicable rebates.

Any non-US citizen who requires an ITIN may obtain one by filling out form W-7 and submitting it, along with the required identification, either directly to the IRS or through an authorized Acceptance Agent or Taxpayer Assistance Center. It isn’t necessary to visit the United States to submit a request for an ITIN, as many countries do have Acceptance Agents, and the IRS does accept form W-7 by mail.

While this might seem like a lot of effort for an identification number you may only use once, take heart: once you’ve received your ITIN, it’s yours for good. The numbers do not expire and are not recycled, so you won’t have to apply for another one, regardless of whether one year or ten has passed since you first received it. You will be able to use it on any form that requires an ITIN, from tax returns to real estate paperwork.

The only time you will be required to give up your ITIN is if you receive a US Social Security Number. If this occurs, you must contact the IRS, either in person or by mail, to inform them that you have received an SSN and would like your tax records combined. Doing so will ensure that you receive credit for all taxes paid, and that any tax refund you’re owed can be paid in full.

Applying for an ITIN might seem like a daunting process, but thankfully, there are tax professionals available to help you. If you’re looking to obtain an ITIN in order to file for a US casino withholding tax refund, US Tax Recovery will help you with the necessary paperwork, and with the entire tax recovery process.