We thought this was common knowledge, but obviously people who dine out didn’t get the memo about tipping on tax.

CNBC posted a hack for saving money at restaurants. TIP LESS. That’s incendiary talk if you don’t explain what you mean, CNBC!

They posted a video “trick” that helps you spend less at restaurants: don’t tip on the tax. Again, we thought that was common knowledge that you don’t have to tip on the grand total, because the tax has nothing to do with food quality and service. But it’s a great reminder!

Likewise, a lot of people think there are better ways to save money than shortchanging your server. And many on Twitter even said you should eat out less if that’s a concern…

WEIGH IN: did you already know this? Is it a concern?