Recently held an event for 27 attendees, was charged the meal, tip and then the tax was added. Is this right?

They’re required by law in the situation you describe.

If you go to a restaurant and order off the menu and then tip the waiter, there is no tax on the tip.

However, if you set up an event where you pay $x per meal and $x as a service charge, most states require that to be taxed. The same goes for a situation where you order and the hotel automatically adds a gratuity or service charge to the bill.