I stay in South Africa so maybe not relevant. From my experience, best to register at the very beginning and take time to setup systems that (a) separate out personal and business expenses and (b) be tax compliant. I started without registering and got myself into several issues related to taxes, and this has proved expensive. The irony is that had I started out with a registered company I would have had a much smaller tax liability. The other advantage is that you are forced to record finances, which means you have to have basic financial systems in place. But, what is VERY important, is to do the registration as quickly as possible, and cheaply.