Director liability: directors of private companies can be jointly and severally liable for unrecoverable tax unless exempted by proof of no gross neglect. Where tax, interest or penalty due from a private company for supplies cannot be recovered, every person who was a director during the relevant period is jointly and severally liable for those amounts unless he proves the non-recovery was not due to gross neglect, misfeasance or breach of duty. If the private company converts into a public company and recovery could not be effected before conversion, that liability provision does not apply to former private-company directors, though any personal penalty on a director remains unaffected.