See which user added a vendor and when

No, QuickBooks does not track the users who added list records.

Surely there must be somewhere this is logged, even if behind the scenes requiring an administrative login?

Hi there, Royce.

I agree with what BRC commented. We cannot track users who added your vendors. 

This feature isn't available yet in QuickBooks Desktop. However, I'd recommend sending feedback to our Product Engineering team so they can add this feature in future enhancements.

Here's how:

1. Go to the Help menu.
2. Select the Send Feedback Online option.
3. Choose the Product Suggestion. You will route to a pop-up window.
4. Type your feedback suggestion in the space provided.
5. Click the Send Feedback button.

Moreover, I've added this article on how to pay your bills online from within the QuickBooks Desktop product: Pay bills online from QuickBooks Desktop.

Feel free to reply to this thread if you need additional assistance managing your vendors in QuickBooks Desktop. Stay safe.

@MAnneJ  RE: However, by filtering the Date Entered/Last Modified option, we can locate in the Audit Trail when were the vendors added.

The Audit Trail report does not show you when vendors were added. The Entered/Last Modified column shows the date the transaction you're looking at was added or modified. Nothing at all to do with the Vendor.

Which you should know.