Tax Field in not showing in Sales Invoice & Purchase order in new recent version
Please provide more information, including a screenshot. Were the fields showing in your previous version?
If you have not done so, you need to set a Tax Code in the Settings tab. See the guide: https://www.manager.io/guides/create-tax-codes/8901
Also, are you referring to Edit or View screen. In View, if no tax is selected, the column does not show.