Most business owners have to deal with paperwork on a daily basis. Some documents, such as invoices and legal agreements, require detailed information about the companies and individuals with whom you're doing business. In some instances, you may need to conduct a tax ID search to verify a company's legitimacy or for filing purposes. Also, it's not uncommon for business owners to lose or misplace their own tax ID number. Knowing where to look for this unique identifier can save you a lot of trouble.

What Is a Tax ID Number?

The IRS requires U.S. businesses to have a tax identification number, or TIN. This unique identifier is used for tax purposes as well as for opening a bank account, filling out forms, hiring employees and more. There are several types of tax ID numbers, including:

  • Employer identification number (EIN) or federal employer identification number (FEIN), which is required for most businesses.

  • Social Security number (SSN), which serves as a tax identification number for sole proprietors and individuals.

  • Individual taxpayer identification number (ITIN), which is required for nonresident aliens and other individuals without a Social Security number.

Solo proprietors, for example, can use their SSN for tax identification purposes. However, if they decide to hire employees, they must apply for an EIN or FEIN. Limited liability companies, partnerships, corporations and other business entities are legally required to have an EIN.

Contact the IRS

Have you lost or misplaced your EIN? Check your bank statements, business registration forms and other documents where this number may be listed. Your previously filed tax returns will include this unique identifier too.

If you don't have access to any of these documents for some reason, contact the IRS at 800-829-4933. This service is available to authorized persons, such as a company's owner, a sole proprietor or a legal representative who has the right to act on behalf of the company.

There are several resources you may use to find another company's EIN or federal tax ID number. Start with the EDGAR database, a free service provided by the U.S. Securities and Exchange Commission. Public companies are required to submit official filings, annual reports and other documents to this database.

To conduct a tax ID search, access SEC.gov and click "Filings." Select "Company Filings Search." Next, enter the company's name, central index key or ticker symbol. If the company is listed in the EDGAR database, you should find its tax ID number within minutes.

Another option is to use EIN Finder, TINCheck, FEIN Search and other online services. These commercial databases allow registered users to conduct a tax ID lookup in exchange for a monthly fee. TINCheck offers a free trial that includes up to three searches. If you need this service on a regular basis, you can sign up for a monthly subscription or purchase a prepaid plan.

Check GuideStar for Nonprofit Data

If you're researching a nonprofit organization, head over to GuideStar. This online database provides information on over 2.7 million nonprofits, including their balance sheet data, revenue and expenses, annual reports and contact details. More than 26 million searches are conducted through this platform each year.

Go to GuideStar.org, click "Search" at the top of the home page and enter the company's name in the designated field. Its EIN will be listed on the right side of the page. You'll also receive its contact information, principal officer's name and National Taxonomy of Exempt Entities code. Register for a free account to access its financial information.

Visit the Company's Website

Check the company's Privacy Policy, Terms of Use and Contact web pages. Some businesses list their federal tax ID number along with their name and address in these sections.

If you still can't find the information you need, contact the company's accounting department. Explain why you need its EIN and make sure you have a valid reason to request this data.