We can perform some fixes so you're able to add invoice numbers in QuickBooks, @FANTA07. Let me provide detailed steps on how to do it.

Before we begin, let's ensure that the Invoice Number option is enabled under the Customise section of your Invoices tab. This will allow you to add a number. If this option is already enabled, we can proceed with performing basic troubleshooting steps.

Performing basic troubleshooting steps can often quickly solve common issues, such as outdated cached files causing features doesn't work as it is. 

First, please open your QBSE account trough private or incognito tab and open your invoices tab.

Here are the keyboard shortcuts:

• Google Chrome: Ctrl + Shift + N
• Microsoft Edge: Ctrl + Shift + N
• Safari: Command + Shift + N
• Mozilla Firefox: Ctrl + Shift + P

If it works, return to your regular browser and clear its cache to remove any unnecessary data and start afresh.  You can consider a different supported browser to optimize your QuickBooks experience.

Additionally, you can check this article on how to run report and export it through CSV file. This will allow you to view and analyze your financial data, aiding in making informed business decisions: Export transactions and get reports in QuickBooks Self-Employed.

By doing basic troubleshooting, we can ensure navigation efficiency, FANTA07. If you have more questions or need further assistance with sales transactions, feel free to contact us. We'll be here