Normally, late fees on a RESIDENTIAL lease or rental agreement would not be considered "rent" and would not be properly included on a 3-day notice to pay rent or quit.
If a landlord proceeds to evict a residential tenant based upon an invalid 3-day notice to pay rent or quit, the tenant can probably file a motion to quash to challenge the allegations of the complaint for unlawful detainer.
A tenant who believes that the landlord has acted unlawfully in giving the tenant a three-day notice or a tenant who may have a valid defense to an unlawful detainer lawsuit should carefully weigh the pros and cons of contesting the landlord's likely unlawful detainer lawsuit against the tenant by consulting with a lawyer, a legal aid organization, tenant-landlord program, or housing clinic.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice for a particular case. This Avvo.com posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult with your own attorney.