(b) Any employer who has once become liable for contributions under this article with respect to persons employed in personal or domestic service in a private home shall cease to be liable as of the first day of the calendar quarter next following the filing of his written application, provided the commissioner finds that the employer has not with respect to such persons paid remuneration in cash of five hundred dollars or more in any of the four calendar quarters preceding such day. 2. Voluntary coverage. Any employer who has elected to become liable for contributions under this article may terminate such liability hereunder after the expiration of the second calendar year of his liability, as of the first day of any calendar quarter, provided he files with the commissioner a written notice of his intent to terminate liability hereunder before the first day of the calendar quarter beginning with which this liability is to terminate. 3. Non-payment of wages. Any employer who has paid no wages for employment in this state during a period of four consecutive payroll years shall cease to be an employer liable for contributions as of the end of the last of such payroll years.