System showing unexpected problem: -37100 when I wanted to save a recurring transaction under bill, the tax code selected was TX.

Hi there, @Jestinna. Thanks for bringing your concern to the QuickBooks Community page.

I'd be glad to share with you some troubleshooting steps to fix the issue and continue with your task in QuickBooks.

Sometimes, too much accumulated cache can cause unexpected behavior with the product. This can be why you're getting the error message when saving your recurring transaction. 

To isolate the problem, let's open your account in a private window. This will help us check if the issue is related to cache build-up. Simply press the following shortcut keys to access this mode:

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

If it works, go back to your regular browser and clear its cache. You can also utilize other supported browsers to fix the problem.

Recurring templates can help you save time. In case you want to update it, feel free to check this resource as your reference:  How to change a recurring transaction template in QuickBooks Online.

Please reply here if you have any other questions about recurring transactions. I'm happy to help so you can continue working in QuickBooks. Have a great day!