Director joint and several liability for unrecoverable company tax unless non-recovery proven not due to gross neglect. A liquidator must notify the Commissioner of his appointment within a short statutory period; the Commissioner, after inquiry, must notify the liquidator of the amount deemed sufficient to provide for any tax, interest or penalty then due or likely to become payable. If tax, interest or penalty determined for any period cannot be recovered on winding up, every person who was a director during that period is jointly and severally liable unless he proves that non-recovery is not due to gross neglect, misfeasance or breach of duty.