Can i add tax to purchase order and invoice in QB

Yes, you can add taxes on both, finance.

Make sure to set up the tax first. Here's how:

1. Click Taxes on the left pane.
2. Select Set up tax.
3. Set up the necessary details ,then select Next.
4. Follow the steps to finish and select Done.

You'll see a Tax/GST column on your sales and purchases forms.

Check this article on how to apply sales tax to transactions: https://community.intuit.com/articles/1775733.

Let me know if you have any questions.