Joint and several liability of LLP partners extends to unpaid tax unless lack of gross neglect is proved. Where tax, penalty, interest, fees or other sums payable are due and cannot be recovered from the LLP or from any person in respect of income of a tax year during which that person was an LLP, every person who was a partner at any time during the relevant tax year is jointly and severally liable for the unpaid amount, unless he proves that the non-recovery cannot be attributed to his gross neglect, misfeasance or breach of duty in relation to the LLP's affairs.