26 CFR 31.3406(h)-1 - Definitions.
(a) In general. For purposes of section 3406 and the regulations thereunder, the definitions of this section apply.
(b) Taxpayer identification number - (1) In general. Taxpayer identification number means the identifying number assigned to a person under section 6109 (relating to identifying numbers, generally a nine-digit social security number for an individual and a nine-digit employer identification number for a nonindividual, e.g., a corporation, partnership, trust, or estate). An obviously incorrect number is not considered a taxpayer identification number. See § 31.6011(b)-2 and § 301.6109-1 of this chapter for provisions relating to obtaining a taxpayer identification number.
(2) Obviously incorrect number. Obviously incorrect number means a number that does not contain nine digits or a number that includes an alpha character as one of the nine digits.
(c) Broker. Broker is defined in section 6045(c)(1) and § 1.6045-1(a)(1) of this chapter. If there could be more than one broker with respect to any acquisition, only the broker having the closest contact (as determined under 1.6045-1(c)(3)(iii) and (iv) of this chapter) with the payee is treated as a broker. In the case of any instrument, the term broker does not include any person who is the payor with respect to the instrument as described in § 31.3406(a)-2.
(d) Readily tradable instrument. Readily tradable instrument means -
(1) Any instrument that is part of an issue any portion of which is traded on an established securities market (within the meaning of section 453(f)(5)); or
(2) Any instrument that is regularly quoted by brokers or dealers making a market.
(e) Day. Day means a calendar day unless specified otherwise under any section of the regulations under section 3406. For example, see §§ 31.3406(d)-5(a) and 31.3406(g)-3(a)(2).
(f) Business day. Business day means any day other than a Saturday, Sunday, or legal holiday (within the meaning of section 7503).