Any LLC or corporation appearing as a party in a lawsuit must be represented by an attorney. A non-lawyer cannot represent a professional services corporation, even if he or she is the corporation’s sole director, officer, and shareholder. This rule applies in eviction cases (a.k.a. unlawful detainer actions), and applies whether the property is commercial or residential.
The Washington Court of Appeals applied this rule a couple of years ago.
A dentist and his commercial landlord were in a long-standing dispute over common area maintenance charges. The commercial landlord served a notice to pay rent or vacate then brought an unlawful detainer action, naming the dentist’s corporation as a defendant—but not the dentist as an individual. The dentist appeared without an attorney.
The lower court ruled that the dentist could not appear for the professional corporation, even though he was the corporation’s sole director, officer, and shareholder. The court entered an order evicting the dentist and a judgment for $43,377.68. The Court of Appeals upheld this result.
If you are a landlord or tenant and enter a rental contract or lease as an LLC or corporation, in court you must be represented by an attorney.
 Cedar Professional Center, LLC v. Bernhardt, unpublished opinion (NO. 63712-6-I November 26, 2012).
 There are some narrow exceptions, such as Small Claims Court. Small Claims Court has no authority to evict a tenant.