Unexpected Internal Error. (-30009) when trying to "resolve" a transaction for a payment made on a bill higher than the bill amount. How can I fix this?

Hello there, @serena3.

Thank you for taking the time posting in the Community. I'd be happy to help share a few troubleshooting steps to get this straightened out.

It's possible, your browser's cache is causing this unexpected behavior. To check if this is a browser-related issue, let's start the troubleshooting by accessing your account using incognito:

• Google Chrome: press Ctrl + Shift + N 
• Mozilla Firefox: press Ctrl + Shift + P
• Internet Explorer: press Ctrl + Shift + P
• Safari: press Command + Shift + N

If you're able to get to "resolve" a transaction for a payment successfully, you'll need to go back to your regular browser and clear its cache by following the steps in this article: How do I clear temporary internet files and cache?.

After that, log in to your QuickBooks Online account again and press CTRL + SHIFT + DEL to bring up the history menu. Make sure all boxes are marked.

For Google Chrome, please set the Time range to All time. Select the Advanced tab and click Clear data. 

Close and sign back in QuickBooks and see if the troubleshooting works. If you're getting the same result, I recommend reaching out to our Customer Care support. 

One of our agents can securely access your account and see what's causing this to happen. You can check out our contact information in the link below: 

Contact the QuickBooks Online Customer Support team.

Feel free to let me know how things go by leaving a comment below. I'll be happy to help you out. Have a great day ahead.