Tax payments can be made to IRAS under 'Invoices' payment flow. You will need to add IRAS as a new supplier. To do this click 'Add Supplier' in the Invoice payment flow and enter the following details:
1. UEN - T08GB0020K
2. Bank - DBS
3. Account Number - 0010468669
4. Note to Supplier - Your Tax Reference Number / 14 Digit Payment Slip Number and Tax Type (i.e. 20150712D Income Tax)
It is important to you indicate both the Tax Reference Number and Tax Type for IRAS reconciliation purposes.
Further details can be found on IRAS site here.