For all income tax purposes, a single-member LLC classified as a disregarded entity must use the owner’s social security number or EIN if the sole member is a partnership, corporation or trust. This includes all information returns and reporting related to income tax. For example, if a disregarded entity LLC that is owned by an individual is required to provide a Form W-9, Request for Taxpayer Identification Number and Certification, the LLC must provide the owner’s SSN or EIN, not the LLC’s EIN.
However, many new single-member LLCs classified as a disregarded entity will need to obtain an EIN for the LLC. An LLC will need an EIN if it has any employees or if it will be required to file any of the excise tax forms. See Form SS-4, Application for Employer Identification Number, for information on applying for an EIN.