(1) The term “compensation” means any form of money remuneration paid to an individual for services rendered as an employee to one or more employers. Such term does not include (i) the amount of any payment (including any amount paid by an employer for insurance or annuities, or into a fund, to provide for any such payment) made to, or on behalf of, an employee or any of his dependents under a plan or system established by an employer which makes provision for his employees generally (or for his employees generally and their dependents) or for a class or classes of his employees (or for a class or classes of his employees and their dependents), on account of sickness or accident disability or medical or hospitalization expenses in connection with sickness or accident disability or death, except that this clause does not apply to a payment for group-term life insurance to the extent that such payment is includible in the gross income of the employee, (ii) tips (except as is provided under paragraph (3)), (iii) an amount paid specifically—either as an advance, as reimbursement or allowance—for traveling or other bona fide and necessary expenses incurred or reasonably expected to be incurred in the business of the employer provided any such payment is identified by the employer either by a separate payment or by specifically indicating the separate amounts where both wages and expense reimbursement or allowance are combined in a single payment, or (iv) any remuneration which would not (if chapter 21 applied to such remuneration) be treated as wages (as defined in section 3121(a)) by reason of section 3121(a)(5). Such term does not include remuneration for service which is performed by a nonresident alien individual for the period he is temporarily present in the United States as a nonimmigrant under subparagraph (F), (J), (M), or (Q) of section 101(a)(15) of the Immigration and Nationality Act, as amended, and which is performed to carry out the purpose specified in subparagraph (F), (J), (M), or (Q), as the case may be. For the purpose of determining the amount of taxes under sections 3201 and 3221, compensation earned in the service of a local lodge or division of a railway-labor-organization employer shall be disregarded with respect to any calendar month if the amount thereof is less than $25. Compensation for service as a delegate to a national or international convention of a railway labor organization defined as an “employer” in subsection (a) of this section shall be disregarded for purposes of determining the amount of taxes due pursuant to this chapter if the individual rendering such service has not previously rendered service, other than as such a delegate, which may be included in his “years of service” for purposes of the Railroad Retirement Act. Nothing in the regulations prescribed for purposes of chapter 24 (relating to wage withholding) which provides an exclusion from “wages” as used in such chapter shall be construed to require a similar exclusion from “compensation” in regulations prescribed for purposes of this chapter.