Hi there, @WC2019. 

Thanks for visiting the Community. I appreciate you for sharing the details of your concern. Based on what you've shared, you did the right thing. Unless you've created an invoice twice. 

Let's run the Profit and Loss by Customer report to verify the transactions. Here's how: 

1. Click the Reports tab on the left panel. 
2. Enter and select Profit and Loss by Customer report. 
3. Customize the date in the Report period drop-down list. 
4. Select the Customize button and click Filter. 
5. Select the customer name in the Customer drop-down list, then Run report. 

Review the transactions in the report. Once you confirmed that there are two items created, select one of them and delete it. 

For more information, I got you an article that can guide you through converting an estimate into an invoice: Set up and use estimates. It also contains links to different topics that will help you with using the estimate.

Let me know if you have other concerns. We're always delighted to assist you some more.