How do i update "invoice" to "tax invoice" on custom field template? the template looks ok, but does not appear on the preview pdf.

It's nice to see you here in the Community, hello221. Let's ensure your invoices have correct headings and labels in QuickBooks Online (QBO).

A tax invoice shows the amount of tax payable on a transaction. In QBO, an invoice will automatically appear as a tax invoice as long as you've chosen either the Exclusive of Tax or Inclusive of Tax option in the Amounts dropdown on the Invoice page.

If you've created a custom form style for your invoices, I recommend reviewing the Content tab of the template page to ensure the name of the Tax Invoice form has been set accordingly. This will ensure that your tax invoice will be labeled precisely. You can also check the other configuration settings to ensure the Tax Invoice heading appears on the invoice.

If you've verified that the template is customized accurately and the PDF preview still doesn't show the Tax Invoice heading, let's perform some troubleshooting steps to isolate the matter. A cache-related issue could be causing some pages not to load correctly.

To begin, open your QBO company in a private browser to allow QuickBooks to start on a clean slate. Then, open a PDF preview of a Tax Invoice you've created. If everything goes smoothly and the Tax Invoice label appears on your end, I suggest going back to your regular browser to clear its cache. Alternatively, you can use other supported browsers.

For more information, I've added this article about tax invoices: What is a tax invoice?

For future use, here's an article on generating reports in QuickBooks to get a comprehensive overview of your taxes and invoices: Run reports.

Come back to this post if you have any other concerns about taxes and invoices in QuickBooks Online, hello221. The Community will always be here to provide further assistance.