Prefixes and IDs are used to reference securities. They're a simple way to organize your cap table. They are not legally required but are useful for keeping your cap table organized.

Typically depends on the type of stock. These can be changed very easily and there’s no legal rule on what to name them.

Here's the convention for prefixes:

Share prefixes are dependent on the share class. Typically, you use CS for Common, PS1, PS2, PS3, etc. for each preferred share class.

IDs are incremental based on the issue date. The earliest issued SAFE gets an ID of 1, then next SAFE gets an ID of 2, etc.