25. Liability of firm. - Notwithstanding any contract to the contrary, where any firm is liable to pay tax under this Act, the firm and each of the partners of the firm shall be jointly and severally liable for such payment:
Provided that, where any such partner retires from the firm he shall intimate the date of his retirement to the Commissioner by a notice in that behalf in writing and he shall be liable to pay the lax and the penalty (if any) remaining unpaid at the time of his retirement and any tax due up to the date of retirement though un-assessed at that date:Provided further that where no such intimation is given within fifteen day from the date of retirement the liability of the partner under the first proviso shall continue until the date on which such intimation is received by the Commissioner.
