A commercial landlord can sue its tenant for breach of a written lease for up to 4 years according to California Code of Civil Procedure section 337, which sets forth the statute of limitations for breach of contract. However, if the lease is oral, then the landlord is limited to a 2 year statute of limitations. The same statute of limitations also applies to a tenant who is suing its landlord for breach of contract. Note, this statute of limitations deals with breach of contract causes of action – not unlawful detainer causes of action.
The key in analyzing the statute of limitations for any cause of action is focusing on the discovery of the actual breach.
Statutes of limitations generally involve some interpretation, so it is always best to bring your claim as soon as possible.