Thank you for joining the thread, IBPAP_Jo. I appreciate your previous steps. Let me make sure that you're properly guided in generating your Vendor Contact List report with the Tax ID included in the customized columns.

Firstly, we need to ensure that we have toggled the Show More option below the gear icon to display your options for the columns you want to include in your report. Here's how we can do it:

1. Go to Reports.
2. Type and click Vendor Contact List in the search field.
3. On the report page, click the Gear icon, then click Show More at the bottom left.
4. Click Tax ID and then Run Report to save the change.
5. Proceed in exporting the Vendor list by clicking the icon on the left side of the Gear icon. 

Here's a screenshot for visual reference:

However, if the issue persists even after following the steps above, I suggest we perform basic troubleshooting on your account to check why this is happening. First, let's review if this is a browser-related issue. Let's start by opening your account in a private browser as it ignores historical data. 

These are the keyboard shortcuts:

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

If the error is fixed after this, then the issue is likely caused by your browser. You'll want to clear your regular browser cache. Another option is to use other supported browsers.

When generating the same reports in the future, you can refer to this article to save time: Memorize reports in QuickBooks Online.

Come back to this thread anytime for more reports and other QuickBooks-related queries. I'll be right here to assist you further. Take care.