What is customer file number irs?

A customer file number (CFN) is a unique identification number assigned to a business or individual by the Internal Revenue Service (IRS). This number helps the IRS keep track of all tax-related matters associated with a particular customer. In general, a CFN is assigned when a customer files their first tax return with the IRS. This number is different from an employer identification number (EIN) or a social security number (SSN), both of which are also used by the IRS to identify taxpayers. CFNs can be helpful when dealing with the IRS on certain issues, such as correcting errors on a tax return or inquiring about a refund.