Hi Newtothis02,

Let me guide you on how you can enable monthly IAS in your QuickBooks Online account. Here's how:

1. Click on the GST tab in QBO.
2. Click on Tax Settings.
3. Select Company income tax (PAYG Instalments).
4. Set reporting frequency to Monthly.
5. Click on Save.

When PAYG monthly reporting is enabled, the first two months of each quarter will show you a Prepare IAS button to lodge. After you've lodged the monthly IAS for the first two months, the Prepare BAS option will show for the quarter.

For reference check this link about: Report PAYG Withholding on BAS and IAS. 

Drop by again in the Community if you have further questions about QuickBooks Online. I'm around to help.