A company's Employer Identification Number changes only when the ownership or organizational structure changes, states the IRS. In most other cases, a company's EIN remains the same from one year to the next.
The structure a company takes determines which EIN regulations it follows, according to the IRS. For example, if the owner of a sole proprietorship takes on a business partner and decides to operate as a partnership, or if the sole proprietorship decides to incorporate or undergoes a bankruptcy proceeding, the owner is required to obtain a new EIN. Different EIN regulations are in effect for sole proprietorships, partnerships, corporations, limited liability corporations, estates and trusts. A complete list of regulations and reasons for changing an EIN is available at IRS.gov.
Also sometimes referred to as a Federal Tax Identification Number, an EIN is a unique identifying number for business entities. Once the IRS assigns an EIN to a business, that number is never used for another business, and the IRS cannot cancel a business's EIN. The IRS considers an assigned EIN permanent, even if the EIN is never used to file Federal tax returns. A person responsible for business entities can apply for an EIN for free online at IRS.gov.