Tax liability expansion: 'tax due' now includes penalties and interest, extending partner liability in LLP liquidations. Where tax cannot be recovered from an LLP or from a person for income of a previous year during which that person was an LLP, every person who was a partner at any time in the relevant year is jointly and severally liable unless he proves non-recovery is not attributable to his gross neglect, misfeasance or breach of duty; the term 'tax due' is clarified to include penalty, interest or any other sum payable under the Act.