rules similar to the rules of sections 51(i)(1) and 52, of the Internal Revenue Code of 1986, shall apply. (4) Employee not taken into account more than once An employee shall not be treated as an eligible employee for purposes of this subsection for any period with respect to any employer if such employer is allowed a credit under subsection (a), or section 51 of the Internal Revenue Code of 1986, with respect to such employee for such period. (c) Employee retention credit for employers affected by Hurricane Maria (1) In general For purposes of section 38 of the Internal Revenue Code of 1986, in the case of an eligible employer, the Hurricane Maria employee retention credit shall be treated as a credit listed in subsection (b) of such section. For purposes of this subsection, the Hurricane Maria employee retention credit for any taxable year is an amount equal to 40 percent of the qualified wages with respect to each eligible employee of such employer for such taxable year. For purposes of the preceding sentence, the amount of qualified wages which may be taken into account with respect to any individual shall not exceed $6,000. (2) Definitions For purposes of this subsection— (A) Eligible employer The term eligible employer means any employer— (i) which conducted an active trade or business on September 16, 2017, in the Hurricane Maria disaster zone, and (ii) with respect to whom the trade or business described in clause (i) is inoperable on any day after September 16, 2017, and before January 1, 2018, as a result of damage sustained by reason of Hurricane Maria. (B) Eligible employee The term eligible employee means with respect to an eligible employer an employee whose principal place of employment on September 16, 2017, with such eligible employer was in the Hurricane Maria disaster zone. (C) Qualified wages The term qualified wages means wages (as defined in section 51(c)(1) of the Internal Revenue Code of 1986, but without regard to section 3306(b)(2)(B) of such Code) paid or incurred by an eligible