Tax for Single occurrence customer order

Jinal, please check Solution ID 225519. It might be due to this limitation. You can ignore that.

Per R&D, "We investigated your issue. It is true that when there is a change related to Single Occurrence Address, it will pop up the mentioned information message. In your test case, it is true that you haven’t done any modification to Single Occurrence address field. It is automatically checked as per CO header settings.
Since CO header level and CO line level has the same address (i.e. Default Check box checked), the application don’t technically identify it as a Single Occurrence Address. Once you unchecked the Default Address check box, the application creates separate Single Occurrence Address line for the CO line. Technically, this is a modification to Single Occurrence Address field and thus trigger the mentioned information message.
It will be tricky to solve this kind of technical designs and require more specific coding. So, we are in a view that your issue can not be categorized as a support level bug."

This is just an Information Message, it will not stop you from saving the single occurrence address.  The IFS application is reminding you to check your tax lines, if needed.  Sales tax is fetched from the customer’s delivery address.  When you enter a single occurrence address, you are no longer using the customer’s delivery address. So the taxes may no longer be valid, so the application is reminding you to check your tax lines. 

There is nothing wrong with what you are doing and there is no specific tax code you need to set up.   If the taxes do not need to be changed, click OK and continue processing your customer order. Please let me know if this answers your question.