No, In Washington state you cannot convert a sole-proprietor businesses into a structured entity (i.e., corporation). You will need to open the corporation as a new business. To do this, you need to complete 3 steps:
1. You first register your new corporation with the Secretary of State's (SOS) Office. You can file online (
https://ccfs.sos.wa.gov/#/), the SOS Office will then issue you a new Unified Business Identifier (UBI) for the corporation.
2. Use the new UBI number to create a new business license through the Department of Revenue using the Business Licensing System (
https://bls.dor.wa.gov/file.aspx).
3. You will also need to reapply for any applicable specialty, and/or city endorsements (for example, Nursery endorsements). You will probably need to re-apply for all of the licenses you currently have. For example, if you are a building contractor, you will need to reapply for your contractor’s license with the Department of Labor and Industries.