My question is about do we have to register our trademark to be valid. 1. can we take a legal action if someone is using similar trademark but our is not registered?
In the US, trademarks do not need to be registered. The owner of the mark can sue in state court for infringement of the trademark without ever registering. However, there is increased protection and specific benefits to registration.
The US Patent and Trademark office (USPTP) PDF publication Basic facts About Trademarks says (on pages 10-11):
In the United States, parties are not required to register their marks to obtain protectable rights. You can establish “common law” rights in a mark based solely on use of the mark in Principal Register provides a number of significant advantages over common law rights alone, including:
• A legal presumption of your ownership of the mark and your exclusive right to use the mark nationwide on or in connection with the goods/services listed in the registration (whereas a state registration only provides rights within the borders of that one state, and common law rights exist only for the specific area where the mark is used);
• Public notice of your claim of ownership of the mark;
• Listing in the USPTO’s online databases;
• The ability to record the U.S. registration with U.S. Customs and Border Protection to prevent importation of infringing foreign goods;
• The right to use the federal registration symbol “®”;
• The ability to bring an action concerning the mark in federal court; and
*The use of the U.S. registration as a basis to obtain registration in foreign countries.
The USPTO is supported in part by fees from trademark applications, and obviously wants to promote registration.
Registration involves fees, and time and expense in preparing the application. It often involves the services of a trademark lawyer. Many businesses find nit worthwhile. Whether it is a good idea for a particular business is an individual, fact-based, business decision, and I cannot advise on it.
In the USA, I know that when someone applies for a trademark, you can complain about it and possibly prevent them from getting the trademark. This will most likely be successful if you have been using say a logo identifying your company in trade, and another company tries to get a trademark for your logo slightly modified, without ever having used it.