Not necessarily, a business can take off from an idea and it is about the business catching up the fire in the market. So if you start doing well you should register your company immediately before someone else takes the name away from you.
But before you start, make sure that the name for your business is available to register. If you do not register, you should register as your brand is in the market and catching the fire.
Absolutely, if you have a long-term plan and you eventually have a great finance to support your business for 2 years. You should get the REGISTRATION done because you might not take the risk of losing the name and investing in the brand image.