20 CFR § 655.12 - Use of registration of H-2B employers.
(a) Upon approval of the H-2B Registration, the employer is authorized for the specified period of up to 3 consecutive years from the date the H-2B Registration is approved to file an Application for Temporary Employment Certification, unless:
(1) The number of workers to be employed has increased by more than 20 percent (or 50 percent for employers requesting fewer than 10 workers) from the initial year;
(2) The dates of need for the job opportunity have changed by more than a total of 30 calendar days from the initial year for the entire period of need;
(3) The nature of the job classification and/or duties has materially changed; or