If you (as an employer) failed to remit payment on or before the 15th of the following month, you can be fined. The minimum fine is RM200 and not more than RM20,000 or 6 months imprisonment or both.
An employer who does not deduct MTD or deducts but fails to remit the MTD to IRBM can be prosecuted in a civil court. With this, the MTD not deducted becomes a debt to the Government.
For more info, you can refer to Inland Revenue Board of Malaysia official portal. 😁