Notwithstanding any contract to the contrary and any other law for the time being in force, where any firm is liable to pay any tax, interest or penalty under this Act, the firm and each of the partners of the firm shall, jointly and severally, be liable for such payment:
Provided that where any partner retires from the firm, he or the firm, shall intimate the date of retirement of the said partner to the Commissioner by a notice in that behalf in writing and such partner shall be liable to pay tax, interest or penalty due up to the date of his retirement whether determined or not, on that date:
Provided further that if no such intimation is given within one month from the date of retirement, the liability of such partner under the first proviso shall continue until the date on which such intimation is received by the Commissioner.