New to QuickBooks Online. Im entering a bill. Once i enter the supplier, to the right it shows a previous balance?? The down to the Category details its blank.

Let's ensure you can enter information in your bill without any issues, 

invermereelectri.

You can turn off the automatic prefill of your forms. To do this, you can follow the steps below:

1. Click the Gear icon.
2. Select Account and Settings.
3. Click Advanced on the left pane.
4. Click the pencil icon on Automation.
5. Toggle to turn off the Pre-fill forms with previously entered content option.
   
6. Click Save and Done.

This should let you enter the information in your bill without any issues. For more information about Accounts and Settings configuration, please check out this article: How Do I set My Advanced Account Settings?

You can also browse and read these help articles for additional references. 

Keep me posted on the process. The Community has always your back if you need anything else. Have a nice day and stay safe!

A quick way to understand this, is because is just pre-filling your new invoice with the previous information you entered, you can change this in your settings, usually a window will pop up tol ask you if you want to prefill or not before entering a new bill.

Hope this helps.

Adriana