Google Patent Application, October 2013: “For example, continuing with the example of FIG. 4, assume that Users A-C have drinks at a bar and User B pays a bill of $45 for the drinks. User B adds the payment transaction as an expenditure of the group and allocates $15 of the transaction to User A, $20 to User B, $10 to User C. In this example, the balance module 308 would update the individual balances of Users A-C to indicate that User B now owes $115 to User A ($130-$15) and User C owes $10 to User B ($0+$10).”

via No joke: Google wants a patent on splitting the restaurant bill – GeekWire.

I didn’t think one could patent a mathematical formula.