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Illinois Late Payment Fee Calculator

Calculate late fees on overdue invoices in Illinois (IL). Compound interest, grace periods, and total amount owed.

Charging late fees on invoices in Illinois depends primarily on what your contract or invoice terms specify. Most Illinois freelancers and small businesses use a monthly interest rate (1–2%) stated up front in their payment terms. Use the calculator below to figure out what's owed on a late invoice.
Calculate Late Fees
Enter your invoice details to calculate the late payment fee

Typical range: 1–2% per month (12–24% annually)

Number of days after due date before late fees apply

Example late-fee calculations in Illinois

$1,500 invoice · 14 days late · 1.5%/mo

Late fee: $10.46

Total owed: $1510.46

$5,000 invoice · 30 days late · 1.5%/mo

Late fee: $75.00

Total owed: $5075.00

$10,000 invoice · 60 days late · 2%/mo

Late fee: $404.00

Total owed: $10404.00

General guidance — not legal advice

Most US states allow contractual late fees that are agreed in writing and "reasonable" for the work performed. The most common contractual rate is 1.5% per month (18% APR) on the unpaid balance, accruing after the invoice due date.

Specific limits and disclosure rules vary by state. For Illinois-specific statutory guidance, consult a Illinois attorney or your state bar association before relying on a particular percentage.

Stop calculating late fees by hand

PrestoBills automatically applies your late-fee policy to overdue invoices, sends payment reminders, and tracks who owes what — for Illinois freelancers and businesses.

First invoice free · No credit card required

Late fees in other states
FloridaPennsylvaniaOhioGeorgiaWisconsinIndianaTennesseeMinnesotaNew YorkCaliforniaTexas

This page is for informational purposes only and is not legal advice. Late-fee rules vary by jurisdiction and contract. Consult a licensed attorney in Illinois for advice on your specific situation.