An Individual Taxpayer Identification Number is a nine-digit number the IRS uses to process taxes and administer tax laws.

"For example, having an EIN for your business ... can qualify if the applicant has a SSN or other taxpayer identification number. You'll answer questions on the IRS website about your business.

The agreement will allow the immigration agency to submit the names and addresses of people living in the United States ...

for example), or take a look at your most recent tax return. The IRS has a handy questionnaire to figure out if you need a Tax ID number, or if you can just use your Social Security number.

For example, the income you receive from ... such as your W-9 containing an improper or incorrect taxpayer identification number. Alternatively, the IRS may notify the payer to start backup ...

Julia Kagan is a financial/consumer journalist and former senior editor, personal finance, of Investopedia. Michael Rosenston is a fact-checker and researcher with expertise in business, finance ...