N.Y. Work. Comp. Law § 55

§ 55. Acceptance of premium by carrier an estoppel. Acceptance of a\npremium on a policy securing to an employee compensation, either alone\nor in connection with other insurance, shall estop the carrier so\naccepting from pleading that the employment of such employee is not a\nhazardous employment or the employment is not carried on for pecuniary\ngain.\n