Check your tax return, W-2, 1099, or other tax documents
Look at official letters from the IRS or your tax authority
Contact your employer’s payroll or HR department
Log in to your online tax account with the IRS or local tax agency
Call the IRS or your country’s tax authority
Search business registration records if you need a company tax ID
Review bank, loan, or vendor paperwork that may list the tax ID
Check state or local tax registration documents
Use the IRS Tax ID Number lookup tools if available for your situation
Request the number from the entity that issued the form or account