GST returns are due one month after the end of the accounting period covered by the return. GIRO deductions are made on the 15th of the month following the due date for GST payments if you are on the GIRO plan.
However, please take note that late GST returns and payments will result in penalties. Therefore, it is important that a GST-registered business needs to monitor its transactions and plan its resources to submit its GST returns on time.