Every bond shall contain a provision substantially to the effect that when the surety exercises its right to withdraw as surety, the withdrawal shall be effective on the first day of the calendar month after receipt of the notice by the Department of Revenue if the notice is received on or before the 15th day of the month, otherwise the withdrawal shall be effective on the first day of the second calendar month after receipt of the notice by the department. [1965 c.525 § 36]