Can you have Sales tax only, when entering a split invoice and I have sales tax only the tax field appears for the expense and it is not able to process, please assist?

Hi there, @finance-sunpower.

Right now, able to have the Sales tax only when splitting an invoice is not an option in QuickBooks Online (QBO).

We recognize that each company has unique needs, and I can see how these features would benefit and empower your business. Since the feature you're looking for isn't currently an option, I encourage you to submit feedback to our Product Development Team. They look through submitted feedback for future updates and use those suggestions to develop changes for the product.

You may also want to visit our QuickBooks Blog. And be the first one to know about any updates that you'll find beneficial for your business. The QuickBooks Blog is our way of letting you know the latest features released and what the product team is working on. They update the site every time new information is available. 

To know more about how splitting transactions work in QBO, see this article: Enter a split transaction into the account history.

If there's anything else you need help with, let me know by adding a comment. I'm more than happy to assist you. Have a great day!