I keep getting an error message to "enter product or service" on a bill, but there is nowhere that asks to enter it. Can someone tell me how/where to enter it?

Good day, @CK737.

Let me help you record your bills in QuickBooks Online (QBO). 

You'll get this error message once you enter any details in the Item details section without selecting a product or service item. 

If you haven't created any items yet, simply follow these steps to add one.

1. Go to the Sales menu and select Product and services.
2. Click New, then choose the type of item you want to create.
3. Add your details and select Save and close.

Once done, create again a bill and select the item in the PRODUCT/SERVICE drop-down list. Enter the rest of the details, then click Save and close.

To know more about tracking bills and recording payments, you can check out this article: Enter and manage bills and bill payments in QBO.

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If you need any further help in managing your expenses in QuickBooks, just add your reply in this thread. I'm always here to help with the process. Have a nice day.