Let me share with you some information about the GST accounts.
QuickBooks Online tracks your GST payment in two separate accounts. It debits the amount to the GST Clearing/BAS Suspense account, and credits the same amount to a bank account. While entering a GST Refund posts the amount as Debit to the Bank account and a Credit to GST Clearing account.
If you're adding transactions from the Banking page, this error means that you cannot assign a GST code when using BAS Liabilities Payable account. The BAS Liabilities Payable, GST Clearing/BAS Suspense and BAS Expense accounts don't need GST codes as these accounts used to track GST and should not be used as nominal accounts.
If you have marked the BAS as lodged for the period where the bank transaction is associated, you can match the bank transaction to the recorded GST Refund.
You can also record a Journal Entry before matching the transactions if you have not been marking the BAS as Lodged.
On the Journal entry, record the following:
Debit: Bank account (the account connected for bank feeds). The amount needs to be exactly the amount shown on the Banking page.
Credit: BAS Liabilities Payable (the account you prefer to use). The same amount above.
Make sure to leave the GST column blank for both Debit and Credit lines. Then, proceed to the Banking page and match the Journal entry to the bank transaction.
For other questions or concerns, please reach out to me. Thanks.