Illinois Late Fee Calculator
Based on 815 ILCS 205/4 (Interest Act); Local Government Prompt Payment Act (50 ILCS 505)
QuickBillMaker applies late fees automatically based on your configured policy. Set it once and stop chasing payments by hand.
How Illinois late fees work
In Illinois, late payment fees on commercial invoices are governed by 815 ILCS 205/4 (Interest Act); Local Government Prompt Payment Act (50 ILCS 505). The legal maximum is 1.5% per month (18% annualized). Standard contract late fee allowed up to 9% per year (0.75%/mo) without written agreement. Higher rates require written contract.
The fee must be stated in a written agreement before the work is performed. Without a written rate, only the statutory default rate applies.
Illinois prompt-pay law
Illinois Local Government Prompt Payment Act (50 ILCS 505); Building and Construction Contract Act (815 ILCS 603) Local gov: payment within 30 days. Construction: 15 days after prime contractor receives payment.
Stop calculating late fees by hand
QuickBillMaker applies your Illinois late fee rate automatically when invoices go overdue.
Automate late fees free