I have incorrectly classifed a transaction as s a 'transfer' and now its showing up on my balance sheet as a fixed asset

Welcome to the Community, sukai. I'm here to provide details to help you correct your transaction in QuickBooks. 

In QuickBooks Online(QBO), you can edit a mistakenly classified transaction by undoing categorisation first and then re-categorise. I'll guide you on how to achieve that through the steps below.

Here's how:

1. Go to Transactions. 
2. Select Bank transactions.
3. Navigate to the Categorised tab.
4. Select the transaction you want to edit, and hit Undo.

Once done, the selected transaction will be in the For review tab. From there, you can re-classify the transaction to the correct category.

Moreover, you can refer to this article to learn more about categorising and matching bank transactions in QBO: Categorise and match bank transactions.

Let us know in the comments if you have further questions about categorising your transactions. We're always here to help you out. Stay safe.