1. I take a picture of the restaurant bill, in case my memory is obstructed by alcohol. 2. Bill people using Venmo. Email then the picture I took. For more co

1. I take a picture of the restaurant bill, in case my memory is obstructed by alcohol. 2. Bill people using Venmo. Email then the picture I took. For more complicated stuff, life travels, I keep a Google Spreadsheets which calculates what each paid, and how much each needs to pay to the others. Then I share it with everyone.