Can a California tenant challenge a rent increase in court?

Yes, in two scenarios. First, if the increase exceeds a statutory rent cap that applies to the unit (where California or local law limits annual increases), the tenant can challenge the excess amount in court or through the local rent board. The remedy is usually rent abatement and refund of overpayment. Second, if the increase notice itself was procedurally defective (insufficient notice period, improper service, missing required disclosures), the tenant can challenge the increase as void and continue paying the old rent until proper notice is served. Both challenges typically require the tenant to first dispute the increase in writing to the landlord. California requires 30 days notice for rent increases of 10% or less and 90 days notice for increases above 10%. AB 1482 caps annual increases at the lower of 5% + local CPI or 10% flat, with exemptions for natural-person single-family owners and buildings under 15 years old. Tenants should consult with a local fair-housing or tenant-rights organization before withholding rent based on a perceived improper increase, as nonpayment can become its own ground for eviction.

Source: Cal. Civ. Code 827(b)