PAYG is often calculated and paid as part of a BAS payment. The PAYG instalment may reduce your entitlement to a refund of GST Paid or increase the amount of a payment due to the ATO.
The first step in posting correctly is to enter the journals required to show the total BAS due to or refundable from the ATO and the appropriate PAYG component.
If you have made the postings required to enter your periodic BAS return correctly, your Fund accounts will either show an amount owed to the ATO or a refund due from the ATO in 2-2100 Sundry Creditors.
When you make your BAS payment or receive your BAS refund, you should allocate it to 2-2100 Sundry Creditors. There is no need to identify the PAYG component separately, as the segregation was taken care of when processing the BAS return.