§ 301.6109-1 Identifying numbers.
(c) Requirement to furnish another's number.
...
When the person making the return, statement, or other document does not know the number of the other person, and has complied with the request provision of this paragraph (c), such person must sign an affidavit on the transmittal document forwarding such returns, statements, or other documents to the Internal Revenue Service, so stating.
§ 31.3406(h)-2 Special rules.
(c) Trusts. Withholding under section 3406 applies to reportable payments made to a trust if any of the conditions for imposing withholding under section 3406 apply to the trust. Generally, a trust is not a payor and will not be required to withhold under section 3406 on reportable payments that it makes to its beneficiary who is subject to withholding under section 3406. The preceding sentence does not apply, however, to a grantor trustdescribed in § 31.3406(a)-2(b)(1) or (2), which is treated as a payor. The trustee of a trust described in this paragraph (c) may certify that the trust's taxpayer identification number is correct and that the trust is not subject to withholding due to notified payee underreporting, without regard to the status of the beneficiaries of the trust.
