Check your tax returns, especially business tax filings
Look at IRS notices or letters sent to your business
Review your original EIN confirmation letter from the IRS
Check business bank account opening documents
Review payroll records or tax forms such as W-2s, 1099s, or 941s
Contact your accountant, bookkeeper, or payroll provider
Search your business records and incorporation documents
Call the IRS Business & Specialty Tax Line at 800-829-4933
Use the IRS EIN online application if you need to apply for a new EIN
Check state business registration records if the EIN was listed there