Legal Question in Business Law in Washington

The only way you can use "Inc" in your company name is to incorporate, which is not really that tough or expensive to do and a good idea for any number of reasons.

If you include "Inc." in your business name and are not incorporated, the net result is minimal or none. When you do business as a corporation (designated by the "Inc." at the end of the business name) you get the benefits of being recognized as a corporate structure, the most significant of which for most is limited (no personal) liability. If you add "Inc." to your business name, and are not incorporated, you don't have the limited liability (you will still have personal responsibility for business debts) but since you apparently were not seeking to use it for that purpose, you have not created a problem for yourself.

Most business planning is not this simple. You will benefit from consulting an experienced business lawyer before starting a new business for many other reasons.