This page includes forms, fees, and instructions for all domestic business entities, foreign and domestic Registered Agents, and Washington Trademarks. An LLC beginning business in Washington State must file formation documents with the Washington Secretary of State.The document required to form an LLC in Washington is called the Certificate of Formation. Forming your Washington LLC requires specific steps to ensure your small business is filed correctly with the state department. I'll show you exactly how to start an LLC in Washington in six steps so while you can do all this yourself I actually recommend using a service like Northwest. Gather your business information: You'll need your LLC's name, registered agent information and details about the structure of your business and its management. When you form a Washington LLC, you file a Certificate of Formation with the Secretary of State. This filing legally creates your limited liability company. There's no filing fee. Washington limited liability company formation requirements from BizFilings.