Wisconsin Late Fee Rules (Wis. Admin. Code ATCP 134.09)

There is no Wisconsin statute capping the amount of a late fee. Wis. Admin. Code ATCP 134.09 controls the practice: 'no landlord may charge a late rent fee or late rent penalty to a tenant, except as specifically provided under the rental agreement.' Before assessing a late fee, the landlord must 'apply all rent prepayments received from that tenant to offset the amount of rent owed.' The rule also bars stacking: 'no landlord may charge any tenant a fee or penalty for nonpayment of a late rent fee or late rent penalty.' So a late fee is enforceable only if it is disclosed in and authorized by the written rental agreement; an undisclosed or compounding late charge is a prohibited practice. Courts may scrutinize an unreasonable fee as an unlawful penalty rather than a genuine charge.

Charging a late fee not provided for in the rental agreement, failing to credit prepayments first, or charging a fee for nonpayment of a late fee violates ATCP 134.09. A tenant may recover double damages plus reasonable attorney fees under Wis. Stat. Sec. 100.20(5).