26 U.S.C. § 3401 : US Code - Section 3401: Definitions

    (a) Wages
      For purposes of this chapter, the term "wages" means all
    remuneration (other than fees paid to a public official) for
    services performed by an employee for his employer, including the
    cash value of all remuneration (including benefits) paid in any
    medium other than cash; except that such term shall not include
    remuneration paid - 
        (1) for active service performed in a month for which such
      employee is entitled to the benefits of section 112 (relating to
      certain combat zone compensation of members of the Armed Forces
      of the United States) to the extent remuneration for such service
      is excludable from gross income under such section; or
        (2) for agricultural labor (as defined in section 3121(g))
      unless the remuneration paid for such labor is wages (as defined
      in section 3121(a)); or
        (3) for domestic service in a private home, local college club,
      or local chapter of a college fraternity or sorority; or
        (4) for service not in the course of the employer's trade or
      business performed in any calendar quarter by an employee, unless
      the cash remuneration paid for such service is $50 or more and
      such service is performed by an individual who is regularly
      employed by such employer to perform such service. For purposes
      of this paragraph, an individual shall be deemed to be regularly
      employed by an employer during a calendar quarter only if - 
          (A) on each of some 24 days during such quarter such
        individual performs for such employer for some portion of the
        day service not in the course of the employer's trade or
        business; or
          (B) such individual was regularly employed (as determined
        under subparagraph (A)) by such employer in the performance of
        such service during the preceding calendar quarter; or

        (5) for services by a citizen or resident of the United States
      for a foreign government or an international organization; or
        (6) for such services, performed by a nonresident alien
      individual, as may be designated by regulations prescribed by the
      Secretary; or
        [(7) Repealed. Pub. L. 89-809, title I, Sec. 103(k), Nov. 13,
      1966, 80 Stat. 1554]
        (8)(A) for services for an employer (other than the United
      States or any agency thereof) - 
          (i) performed by a citizen of the United States if, at the
        time of the payment of such remuneration, it is reasonable to
        believe that such remuneration will be excluded from gross
        income under section 911; or
          (ii) performed in a foreign country or in a possession of the
        United States by such a citizen if, at the time of the payment
        of such remuneration, the employer is required by the law of
        any foreign country or possession of the United States to
        withhold income tax upon such remuneration; or

        (B) for services for an employer (other than the United States
      or any agency thereof) performed by a citizen of the United
      States within a possession of the United States (other than
      Puerto Rico), if it is reasonable to believe that at least 80
      percent of the remuneration to be paid to the employee by such
      employer during the calendar year will be for such services; or
        (C) for services for an employer (other than the United States
      or any agency thereof) performed by a citizen of the United
      States within Puerto Rico, if it is reasonable to believe that
      during the entire calendar year the employee will be a bona fide
      resident of Puerto Rico; or
        (D) for services for the United States (or any agency thereof)
      performed by a citizen of the United States within a possession
      of the United States to the extent the United States (or such
      agency) withholds taxes on such remuneration pursuant to an
      agreement with such possession; or
        (9) for services performed by a duly ordained, commissioned, or
      licensed minister of a church in the exercise of his ministry or
      by a member of a religious order in the exercise of duties
      required by such order; or
        (10)(A) for services performed by an individual under the age
      of 18 in the delivery or distribution of newspapers or shopping
      news, not including delivery or distribution to any point for
      subsequent delivery or distribution; or
        (B) for services performed by an individual in, and at the time
      of, the sale of newspapers or magazines to ultimate consumers,
      under an arrangement under which the newspapers or magazines are
      to be sold by him at a fixed price, his compensation being based
      on the retention of the excess of such price over the amount at
      which the newspapers or magazines are charged to him, whether or
      not he is guaranteed a minimum amount of compensation for such
      services, or is entitled to be credited with the unsold
      newspapers or magazines turned back; or
        (11) for services not in the course of the employer's trade or
      business, to the extent paid in any medium other than cash; or
        (12) to, or on behalf of, an employee or his beneficiary - 
          (A) from or to a trust described in section 401(a) which is
        exempt from tax under section 501(a) at the time of such
        payment unless such payment is made to an employee of the trust
        as remuneration for services rendered as such employee and not
        as a beneficiary of the trust; or
          (B) under or to an annuity plan which, at the time of such
        payment, is a plan described in section 403(a); or
          (C) for a payment described in section 402(h)(1) and (2) if,
        at the time of such payment, it is reasonable to believe that
        the employee will be entitled to an exclusion under such
        section for payment; or
          (D) under an arrangement to which section 408(p) applies; or
          (E) under or to an eligible deferred compensation plan which,
        at the time of such payment, is a plan described in section
        457(b) which is maintained by an eligible employer described in
        section 457(e)(1)(A),(!1) or


        (13) pursuant to any provision of law other than section 5(c)
      or 6(1) of the Peace Corps Act, for service performed as a
      volunteer or volunteer leader within the meaning of such Act; or
        (14) in the form of group-term life insurance on the life of an
      employee; or
        (15) to or on behalf of an employee if (and to the extent that)
      at the time of the payment of such remuneration it is reasonable
      to believe that a corresponding deduction is allowable under
      section 217 (determined without regard to section 274(n)); or
        (16)(A) as tips in any medium other than cash;
        (B) as cash tips to an employee in any calendar month in the
      course of his employment by an employer unless the amount of such
      cash tips is $20 or more; (!2)

        (17) for service described in section 3121(b)(20); (!2)
        (18) for any payment made, or benefit furnished, to or for the
      benefit of an employee if at the time of such payment or such
      furnishing it is reasonable to believe that the employee will be
      able to exclude such payment or benefit from income under section
      127, 129, 134(b)(4), or 134(b)(5); (!2)
        (19) for any benefit provided to or on behalf of an employee if
      at the time such benefit is provided it is reasonable to believe
      that the employee will be able to exclude such benefit from
      income under section 74(c), 108(f)(4), 117, or 132; (!2)
        (20) for any medical care reimbursement made to or for the
      benefit of an employee under a self-insured medical reimbursement
      plan (within the meaning of section 105(h)(6)); (!2)
        (21) for any payment made to or for the benefit of an employee
      if at the time of such payment it is reasonable to believe that
      the employee will be able to exclude such payment from income
      under section 106(b); (!2)
        (22) any payment made to or for the benefit of an employee if
      at the time of such payment it is reasonable to believe that the
      employee will be able to exclude such payment from income under
      section 106(d); or
        (23) for any benefit or payment which is excludable from the
      gross income of the employee under section 139B(b).

    The term "wages" includes any amount includible in gross income of
    an employee under section 409A and payment of such amount shall be
    treated as having been made in the taxable year in which the amount
    is so includible.
    (b) Payroll period
      For purposes of this chapter, the term "payroll period" means a
    period for which a payment of wages is ordinarily made to the
    employee by his employer, and the term "miscellaneous payroll
    period" means a payroll period other than a daily, weekly,
    biweekly, semimonthly, monthly, quarterly, semiannual or annual
    payroll period.
    (c) Employee
      For purposes of this chapter, the term "employee" includes an
    officer, employee, or elected official of the United States, a
    State, or any political subdivision thereof, or the District of
    Columbia, or any agency or instrumentality of any one or more of
    the foregoing. The term "employee" also includes an officer of a
    corporation.
    (d) Employer
      For purposes of this chapter, the term "employer" means the
    person for whom an individual performs or performed any service, of
    whatever nature, as the employee of such person, except that - 
        (1) if the person for whom the individual performs or performed
      the services does not have control of the payment of the wages
      for such services, the term "employer" (except for purposes of
      subsection (a)) means the person having control of the payment of
      such wages, and
        (2) in the case of a person paying wages on behalf of a
      nonresident alien individual, foreign partnership, or foreign
      corporation, not engaged in trade or business within the United
      States, the term "employer" (except for purposes of subsection
      (a)) means such person.
    (e) Number of withholding exemptions claimed
      For purposes of this chapter, the term "number of withholding
    exemptions claimed" means the number of withholding exemptions
    claimed in a withholding exemption certificate in effect under
    section 3402(f), or in effect under the corresponding section of
    prior law, except that if no such certificate is in effect, the
    number of withholding exemptions claimed shall be considered to be
    zero.
    (f) Tips
      For purposes of subsection (a), the term "wages" includes tips
    received by an employee in the course of his employment. Such wages
    shall be deemed to be paid at the time a written statement
    including such tips is furnished to the employer pursuant to
    section 6053(a) or (if no statement including such tips is so
    furnished) at the time received.
    (g) Crew leader rules to apply
      Rules similar to the rules of section 3121(o) shall apply for
    purposes of this chapter.
    (h) Differential wage payments to active duty members of the
      uniformed services
      (1) In general
        For purposes of subsection (a), any differential wage payment
      shall be treated as a payment of wages by the employer to the
      employee.
      (2) Differential wage payment
        For purposes of paragraph (1), the term "differential wage
      payment" means any payment which - 
          (A) is made by an employer to an individual with respect to
        any period during which the individual is performing service in
        the uniformed services (as defined in chapter 43 of title 38,
        United States Code) while on active duty for a period of more
        than 30 days, and
          (B) represents all or a portion of the wages the individual
        would have received from the employer if the individual were
        performing service for the employer.