Im a new user and I want to know best way to see if a bill has been entered twice

Hi there, denise-karibo.

The best way to review bills is by running either the Unpaid Bills or Bills and Applied Payments reports. I'm here to guide you through the steps:

1. Click the Reports tab.
2. Enter and select Unpaid Bills or Bills and Applied Payments reports.
3. Click the Customize button.
4. Filter the Report period.

When you're ready to record bill payments, you can check this guide:  Enter bills and record bill payments in QuickBooks Online.

I'd also recommend reconciling your accounts to effectively manage your transactions and detect any possible errors accordingly. For the step-by-step guide, please check out this article: Reconcile an account in QuickBooks Online.

You can keep me posted on how it goes in the comments below.