Governor Thawar Chand Gehlot assented to the Ordinance draft the cabinet recently cleared.
The Centre has already completed its part by amending the laws by placing the bills before the Parliament, last month.
The GST Council, at its meeting on July 11, decided to tax online gaming, casinos and racecourse at 28% on the full-face value of bets. At a subsequent meeting on August 2, the council decided to complete the process of amendments at the earliest and give effect to them from October 1.
The Karnataka government will on Saturday issue a notification mentioning the date from which the new SGST rate will come into effect, responding to notifications from the ministry of Finance (MoF) on the date of implementation of the new CGST rate.