It's great that you did that, but in my experience (and many freelancers I know) there was not a definitive "I will now become a freelancer" moment.

I had moved to a new city and was interviewing around. A old friend approached me in desperation, offering a lot to work on one-time project for his company. That led to more offers, and those to more. Meanwhile I and friend were building prototypes around a business we might start. (So glad we didn't try to start that one!) Meanwhile, it wasn't until I did my taxes the next year that it hit me that I was now a freelancer.

Only then did I start to get my act together with billing and the rest.