All registered businesses in Ontario must have a business registration number, also called a master business Llcense number. If the business is a sole proprietorship—a business owned and operated by a single individual—you can search for the number online through the Service Ontario website. A fee applies for every search. If the business is a corporation, you can find the business registration number by calling Service Ontario's Companies Helpline at 800-361-3223. The information clerk will be able to give you the corporate business registration number over the phone.

Go to the "Business" home page of Service Ontario's website (see Resources).

Select "Register or Renew Your Business" from the main page.

Scroll down the page and click on "Do It Online Now."

Read and agree to the contents of the client consent form, then click "Next."

Select "Enhanced Business Name Search" and "English," then click "Next."

Click "Next" after reading the information on fees.

Enter the business name in the space provided, choose "Detailed Business Name Report" from the drop-down menu, then click "Next."

Pay the fee by entering your credit card number. Visa, MasterCard and American Express are all accepted. The fee is $8 as of 2010.

Receive your report, which should appear on your computer screen immediately. If you receive a "Statement of No Match," it means the company name you entered was never registered or the company has allowed its registration to lapse. A "Business Name Report" will list the business name and its business registration number, along with other information about the business. Both reports are provided in PDF format so that you can download them to your computer and print them if necessary.