I CLICKED THE OLD STYLE INVOICE TAB AT THE TO AND NOW THERE'S NO WAY TO GO BACK

I've got your back, and I'll help you get this sorted out so you can use the new invoice format again, @DFORSYTH.

Once we switch back to the old invoice layout, we still have the option to go back to the new format. All you have to do is simply open again the sales transaction and click Try the new invoices from the upper right corner of the screen. Then, select again Try new invoice.

See the screenshot below for your reference. 

 You can also check out this article for more info: See what’s new with estimates and invoices in QuickBooks Online.

If you're still unable to see the option to switch invoice layouts, I recommend performing some basic troubleshooting steps. Let's start by opening an incognito window to fix the issue. You can use these shortcut keys below.

• Press Ctrl + Shift + N (Google Chrome)
• Ctrl + Shift + P (Firefox)
• Control + Option + P (Safari)

Also, please make sure that you're using a supported and up-to-date browser to make sure that QuickBooks runs smoothly.

Please keep us posted if you have other questions or concerns about managing your  invoices in QuickBooks.