Hello @jazzarais thanks for your post. Do you have tax rates already setup? You can setup different tax rates and apply them according to your location, or edit your current tax rate. Go to your Dashboard >> Account and Settings >> Business >> Sales Tax. I hope this helps answer your question.

Also check and make sure the item or service you created, that you are adding to the invoice, is set as a "taxable" item. I hope this helps answer your question.