Entering data to a sales invoice to the order number section save. When you reopen the sales invoice the order number section data is no longer there.Why need assists?

Welcome to the Community, Luigi.

I'll be helping you to show the order number section data when accessing sales invoices.

Before anything else, would you mind sharing a screenshot of where the issue occurs? so that we can further help you in resolving this.'

If you mean the Invoice number section in the Sales tab, you must tick the Invoice number column to show it. Here's how:

1. Go to Sales. Then, Invoices.
2. In the right corner, click the Settings icon beside the Action column.
3. Tick the Invoice number box.

Also, you should turn on the Custom transaction numbers in the Account and Settings, then Sales. Never forget to Save, then Done. Check out the screenshot below:

In the meantime, we can perform some basic troubleshooting steps to determine if this is a browser-related concern. First, log in to your QBO account through incognito mode or private browsers to avoid cache files that cause odd behaviors when running web-based programs.

You can utilize the shortcut keys below: 

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

After that, access the sales invoice and look for the order number data. If this works, clear the cache of your regular browser to remove accumulated data. If the issue persists, use another supported browser or device. It might be that the current one you're using has a temporary issue with the program.

You might want to modify the display preference of your sales forms. Check out this article: Customise sales forms by location in QuickBooks Online.

Let me know if you have additional questions about invoices. I'll be willing to lend a hand. Keep safe always.