An application error has occurred while processing your request : -20200
Thank you for dropping your question here in the Community, @jamie37.
Let me help you perform some basic troubleshooting steps that will help you get back to your business.
If you receive an error in QuickBooks Online, I recommend clearing your cache browser. A web page issue might be causing this error to appear. Clearing cache will also help you to have the best and most secure experience with QuickBooks Online
To do that, here’s how.
Select the Menu: button.
Select Site settings under Privacy and Security.
Select Cookies and site data.
Select See all cookies and site data.
Type “intuit” in the search bar to find Intuit cookies.
Restart Google Chrome for the changes to take effect.
You can also use private/incognito or other browsers to login to your QuickBooks Online.
Please know that it will be much appreciated if you will give me more information so I can give you an accurate resolution regarding this concern.
You may also use this article for your future reference if you need some steps or procedures while using QuickBooks Online. Help article.
Feel free to fill me in if you have any other questions. Have a nice day!