Question: When should you trademark your business name?
Answer: Immediately. A trademark application for a business name should be filed as soon as possible because the filing date of your federal trademark application becomes the federal priority date of your trademark.
This means that if you file a trademark application on January 1, and somebody else files for or starts using a similar trademark on January 15, your rights will always be retroactive to January 1. Therefore, as long as your trademark successfully registers, you can enforce it against the person that filed for or used the trademark after you.
On the other hand, if someone else beats you to the market or files the application before you, you could potentially spend tens of thousands of dollars in legal fees trying to oppose the application or sue that person in court. Moreover, you might not even win the case.
Registering for a trademark sooner, rather than later, can prevent major problems from occurring and could potentially save you a lot more money in the long run.