Your federal ID number, or EIN, identifies your business in the same way a Social Security number identifies a person. You need this number to conduct routine business activities, such as open bank accounts, apply for credit, file tax returns, pay employees and apply for licenses. When you misplace your EIN, you can check several sources to find out what it is.

1. Check Your Tax Returns

When you file income or employment tax returns, your EIN is listed on the forms. Check any return previously filed by your business, and look for the spot where your business information is listed. Your EIN is located near the name and address of your company.

2. Check IRS Correspondence

When you apply for an EIN, the IRS issues a letter that contains the number. However, if you've misplaced that letter, most IRS correspondence sent to your business also shows your company's EIN. Look for any IRS notices, bills or general correspondence. Your EIN may be near the top where your company's information appears, or included on any "response vouchers" attached to the letter.

3. Ask Someone Who Handles Your Finances

If the thought of digging through paperwork sounds more tedious than you prefer, check with someone who handles your company's finances, such as your accountant or banker. These professionals use your business EIN to file tax returns and other documents, as well as maintain bank records. Your EIN is attached to these activities, so these professionals have access to the information you need.

4. Call the IRS

The IRS can also provide you with your EIN. Call the IRS Business and Specialty Tax Line, at 800-829-4933 Monday through Friday from 7 a.m. to 7 p.m. local time. The IRS will ask some verification questions to ensure you're an authorized representative of the company before providing the EIN. Owners, officers and members listed on IRS records for the business are automatically authorized to receive this information after verification questions are answered successfully.