IRS Form W-9 (PDF) is the standard form published by the Internal Revenue Service (IRS) used by payers to request Taxpayer Identification Number (TIN) information.
In general, requests for UC Berkeley's TIN are made by payers in order for them to properly report information to the IRS in connection with miscellaneous payments made to the university (interest, dividends, rents, royalties, etc.) or by donors to enable them to claim tax deductions for gifts and donations made to the university.
If your department receives a request for UC Berkeley's TIN, respond to the requesting party by sending them a copy of a completed and signed W-9 that indicates UC Berkeley's TIN.
Questions concerning Form W-9 should be addressed to the Accounts Payable Office at disburse@berkeley.edu.