"Base year" with respect to each individual, shall mean either the first four of the last five completed calendar quarters or the last four completed calendar quarters immediately preceding the first day of the individual's benefit year.
For the purposes of establishing a benefit year, the department shall initially use the first four of the last five completed calendar quarters as the base year. If a benefit year is not established using the first four of the last five calendar quarters as the base year, the department shall use the last four completed calendar quarters as the base year.
Computations using the last four completed calendar quarters shall be based on available wage items processed as of the close of business on the day preceding the date of application. The department shall promptly contact employers to request assistance in obtaining wage information for the last completed calendar quarter if it has not been reported at the time of initial application.