Created in 2036 legally everyone is supposed to have a System Identification number. One is assigned at every birth and they should make everything in life easier. A SIN keeps a legal record of almost every action you do in your life. Need to get on a bus, your SIN will identify you and deduct the fee from your online account. Want to vote in an election, Your SIN will make sure that you help determine who the next president of UCAS will be. Want to get some bread, milk, a shitty apartment? Well Your going to need to use your SIN for that. Wait you don’t have one? You were born in a sprawl outside of a corporate district? You had yours erased during the ‘64 crash? Hell maybe some hacker thought it would be fun to erase you from databases. If you don’t have a SIN you are shit out of luck. You could go apply for a probationary SIN either at a corporation or a government, because everyone wants to be a second class citizen no? While it is illegal to not have a SIN, if your a runner well the less traces there are of your existence the better. Obviously it is illegal to possess a forged SIN or another person’s SIN, but frankly you are going to need an identity. In fact if you want to survive more than a year you will probably burn through several. In point of fact all of this SIN business helps you, Big Brother has so much data coming at him constantly that everyday violations like using your forged SIN to buy food will almost never be noticed. Trying to pass as a head of Security for Saeder-Krupp in a lab for their new prototype orbital habitat, thats going to end differently. The key is to use the information glut to your advantage, if you make it hard enough to sort through all that excess data to find out who you are and what you do then you can hide in plain sight. Piss the right person off enough though and well they are technically killing someon who never existed.