But it's the norm and expectation. Theres a reason why the post tax total is the biggest number on the check. (Other than thats how much you owe)

Agree. It is the norm. All restaurants, the most common places to tip, do this too. If they calculate/print suggested tip amounts they use post tax and also if you trigger a gratuity included they use post tax.

To be far, I think most people use post tax when calculating tip in their head too.

One thing I hear a lot is to just double the sales tax. Around CA, when it was around 7.5%, it added up to a nice 15%. Since they recently increased sales taxes to about 8.5-9% depending on the city, it doesn't work that way. Or yes, if you account for tip inflation.

One thing I saw recently is that a place did 18, 20, 22%. I'm pretty sure I tipped lower just for that.

> If they calculate/print suggested tip amounts they use post tax

I see it done both ways.