We have spoken with the manager on several occasions and told them the service was unacceptable and didn't see why we should be required to pay 18% extra, and in every case they have adjusted it once we explained the problems to them.

They want to know, they want to provide good service. I think many times with large parties the waitstaff doesn't feel they need to work for their tip, as most people just pay whatever they put on the bill.

I calculate the tip pretax. Indeed many of the double or triple the tax to estimate the tip in this area (triple the tax in Connecticut for example would be 18%, based on pretax amount, double in Manhattan would be 16.75%) and that is based pretax.