Depending on your reason for applying for the ITIN number, the required documentation differs. The required documentation, regardless of the reason for application, is: The necessary documentation you can download here. The U.S. Internal Revenue Service issues ITIN numbers to allow individuals to file a tax return, make a refund, or pay payroll taxes if they do not qualify for a Social Security Number (SSN). No. If you have an ITIN number and in the meantime exercise the right to work in the USA, you must apply for an SSN and report to the U.S. Tax Administration so that previous activities with your ITIN number can be linked to your SSN. The main difference between the SSN and the ITIN number is that the SSN is issued to American citizens and non-citizens who have the right to work in the USA, while the ITIN is issued to non-American citizens who are required to file a tax return with the IRS. If you have an ITIN number, and in the meantime, you are eligible for an SSN, the IRS will associate your ITIN with the SSN. The SSN then becomes the primary number and is used for all future tax returns. You can apply for an ITIN number at any time during the year. From the date of sending the request for the issuance of the ITIN number, the IRS leaves a period of 6-12 weeks to process the request and issue the ITIN number. The ITIN number is valid for three years from the date of issue. Each additional tax return extends the activity of the ITIN number for an additional three years. You must renew your ITIN number if you have not filed a federal U.S. tax return using your ITIN number for the past three years. If your ITIN number has expired and you submit a request to the IRS with that number, the request will be processed and treated as sent in a timely manner. However, you will receive a letter of notification from the Tax Administration that there will be a delay in processing the request due to the renewal of the ITIN number. Yes, you can. If you want to file a tax return, you must enter your ITIN number in the SSN space on the tax form. There are two ways to get money from the US tax: