Service of notice for discontinued business treated as notice under general assessment provisions, directed to relevant former persons. Assessment for a discontinued business permits serving a notice on the person whose income is to be assessed, on any individual who was a member of the firm or association at the time of discontinuance, or on the principal officer of a company. The notice may include any requirements ordinarily found in a general assessment notice and, insofar as applicable, the provisions of the Act apply as if the notice were issued under those general notice provisions.