While creating an invoice we are receiving this error message "An application error has occurred while processing your request". How can we fix this?

Good morning, @scottportables. 

Thanks for taking the time to reach out to the QuickBooks Community. 

Let's try some basic troubleshooting steps to clear the error message, such as using an incognito/private browser. I've included some keyboard shortcuts you can use to open the browser below. 

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

If you notice the error message has cleared when trying to create an invoice while using an incognito browser, you'll need to clear the cache of your browser. Web browsers collect cache to save time when loading repetitive data and images. Over time these files can become outdated and corrupted, causing issues like the one with your error message. 

Please let me know if the error message persists. I'm always around if you have any additional questions or concerns. Take care!