EIN stands for Employer Identification number. This number is issued by IRS (Internal Revenue Services). An entity once registered in the United Sates has to apply for EIN. A foreign entity for example a Canadian corporation doing business in the United States can apply for EIN. You can apply for EIN on form SS-4, complete this form, sign it and mail it to IRS. You can also apply for EIN online or call IRS to get your EIN. All entities when filing a tax return or when paying taxes in the United States must mention their EIN on the tax document.