The rules
Split the four of you into two teams before you tee off. Both golfers on a team play their own ball all the way out — there is no best ball and nothing to concede. At the end of the hole each team makes a number out of its two scores, and the two numbers are compared.
The margin is the difference between the numbers, not one point for the hole. That is the whole character of the game: a routine hole is worth eight or ten points, and a hole where somebody loses a ball is worth fifty.
Building the number
One rule, and one exception that comes up more than you would think.
The flip
A birdie by anybody on your team reverses the other team’s number. Their 47 becomes 74. Nothing changes about your own number — you just make theirs as expensive as it can be. This is what turns Las Vegas from arithmetic into a gambling game, and it is the rule most groups get wrong on the first tee.
Scoring, worked all the way through
Paul and Dave against Sam and Lee, at ten cents a point — the three holes from the diagram above.
Picking a stake
The one thing to get right before you tee off. Points in Las Vegas run an order of magnitude higher than in any other golf game, so the per-point number has to be an order of magnitude lower. Ten cents a point is the standard.
House rules worth agreeing on the first tee
Las Vegas has more variants than most, because every group finds its own way to cap the damage. Settle these before you start.
Scoring Las Vegas without doing the arithmetic
Las Vegas looks easy and is not. Every hole you have to order two pairs of digits, check whether a ten belongs in front, work out who birdied and whose number it flips, subtract, and then add a two-digit result to a running total that is already in the hundreds. Miss a flip on the fourth hole and the number in the car park is wrong.
Halved does that part. Post gross scores like any other round. It builds both numbers, applies the flip, keeps the running total in dollars, and shows the whole group the same figure.
Play Las Vegas. Let something else keep score.
Free for the group, flips applied automatically, and the settlement is done before you get to the car park.