Because I'm cheap and I don't earn an income for my work as a SAHM, I usually just pay my exact portion with tax and tip. Sometimes I can afford to put in a little extra, but since we're all adults that decided to go out to eat together, we understand that we are responsible for ourselves. If we bring our kids with us and we're going out with a childless party, it sure doesn't make sense to split the bill evenly when we're feeding a family of 4 and they are a party of only 1 or 2. When going out to drink (which rarely happens anyway) we usally just take turns buying rounds so it all evens out.