Illinois Late Fee Calculator
Your late fee
$62.50
Paid 12 days late; the lease has no grace period.
- Days past due
- 12 days
- Grace period ends
- No grace period
- Earliest fee date
- September 29, 2026
- Lease late fee
- 5% of $1,250.00 = $62.50
- Rent + late fee
- $1,312.50
Illinois: 765 ILCS 705 to 755; 735 ILCS 5/Art. IX contains no late fee provision, so there is no legal cap or waiting period to apply; only your lease terms count.
Next step: turn these figures into a late rent notice for the tenant.
Mobile home parks in Illinois
This covers mobile home park or manufactured home community leases only: such a lease cannot permit a penalty fee for late rent unless the tenant is given at least 5 days past the due date to make the payment.
Sec. 12. Lease prohibitions. No lease hereafter executed or currently existing between a park owner and tenant in a mobile home park or manufactured home community in this State shall contain any provision: (a) Permitting the park owner to charge a penalty fee for late payment of rent without allowing a tenant a minimum of 5 days beyond the date the rent is due in which to remit such payment;
Illinois rent late fee law
Illinois has no statewide late fee cap or grace period for ordinary residential leases in its landlord and tenant acts; mobile home parks have a separate rule.
Read in full for this check: Illinois Compiled Statutes, chapter 765, the Landlord and Tenant acts (765 ILCS 705 to 755), and 735 ILCS 5/Article IX (Eviction). Official source, read from the copy archived on 2026-09-11 · checked .
Late rent notice builder
Before you send it: this builds a reminder letter about overdue rent and a late charge. It is not an eviction notice. A notice to pay rent or quit is a separate document, and Illinois has its own rules for it. Nothing on this page is legal advice.
[Your name or company]
Date: October 10, 2026
To: [Tenant name]
[Rental property address]
Re: Overdue rent for [Rental property address]
Dear [Tenant name],
This letter is a reminder that the rent of $1,250.00 for [Rental property address] was due on September 28, 2026. As of October 10, 2026, $1,250.00 of it is still unpaid (12 days past due).
Your lease provides for a late charge, which comes to $62.50.
Amount now due
- Unpaid rent
- $1,250.00
- Late charge
- $62.50
- Total
- $1,312.50
Please pay $1,312.50 at your earliest opportunity.
If this letter crossed with your payment, please disregard it.
Regards,
[Your name or company]
How to use the Illinois rent late fee calculator
- Enter the monthly rent and the rent that is overdue.
- Enter the date the rent was due and the date it was paid, or today if it is still unpaid.
- Choose how the lease sets the late fee (percent of rent, flat amount or dollars per day) and type the figure from the lease.
- Enter the grace days written in the lease.
- Read the late fee and the earliest fee date, then copy the figures or print a late rent notice.
Work out interest on an overdue B2B invoice under Illinois law. The legal default rate — what applies when the contract is silent — is 5%, and the statute is quoted verbatim below. All math runs locally in your browser.
Statutory legal rate on written instruments and money wrongfully withheld when no rate is agreed.
Late fee breakdown
- Interest owed
- —
- Daily rate
- —
- Total (invoice + interest)
- —
Still unpaid? Generate a formal demand letter — it computes the interest and cites Illinois's statute (815 ILCS 205/2, 205/4) for you.
Worked example: Illinois invoice interest at 5%
Interest at Illinois's statutory default of 5% a year, worked out with the same formula as the calculator above: amount × (5% ÷ 365) × days. If your contract states its own rate, enter that rate in the calculator instead.
| Invoice amount | 30 days late | 60 days late | 90 days late |
|---|---|---|---|
| $1,000.00 | $4.11 | $8.22 | $12.33 |
| $5,000.00 | $20.55 | $41.10 | $61.64 |
| $10,000.00 | $41.10 | $82.19 | $123.29 |
What Illinois law says about invoice interest
Creditors shall be allowed to receive at the rate of five (5) per centum per annum for all moneys after they become due on any bond, bill, promissory note, or other instrument of writing; on money lent or advanced for the use of another; [...] and on money withheld by an unreasonable and vexatious delay of payment.
Quoted verbatim from the linked official source — not our paraphrase. How we source and re-check every row is documented in the data methodology.
Maximum late fee in Illinois — written B2B contracts
No statutory cap
9% nominal cap, but any loan to a corporation and any business-purpose loan may bear any agreed rate. Ordinary B2B credit is effectively uncapped.
Basis: 815 ILCS 205/4(1)(a),(c). Compare all 51 jurisdictions in the maximum late fee by state table and cap-regime map.
Rent and invoices follow different laws — consumer debt is not covered
The Invoice tab, the rate card and the statute sections on this page are about business-to-business invoices. Residential rent late fees live in Illinois's landlord-tenant law. Illinois: 765 ILCS 705 to 755; 735 ILCS 5/Art. IX contains no late fee provision, so there is no legal cap or waiting period to apply; only your lease terms count. Consumer credit has separate, stricter rules. The distinction is explained in B2B invoice late fees vs. residential rent.
Use this data
Illinois's row — rate, cap, citation, verbatim quote, verification date — is part of our open 51-jurisdiction dataset: CSV · JSON (CC BY 4.0, cite myinvoicetemplate.com). Set late-fee terms on your next invoice with the free invoice generator, or state them clearly using the wording guidance in the payment terms guide.
Illinois late fee FAQ
Is there a legal limit on rent late fees in Illinois?
Illinois has no statewide late fee cap or grace period for ordinary residential leases in its landlord and tenant acts; mobile home parks have a separate rule. Read in full for this check: Illinois Compiled Statutes, chapter 765, the Landlord and Tenant acts (765 ILCS 705 to 755), and 735 ILCS 5/Article IX (Eviction), checked 2026-09-29. The late fee and grace days in the lease decide.
How do I work out a late fee on rent in Illinois?
Enter the monthly rent, the overdue amount, the date the rent was due and the date it was paid, then the late fee in the lease (a percent of rent, a flat amount or dollars per day) and its grace days. The calculator gives the late fee, the earliest fee date and rent plus fee, and turns them into a late rent notice.
Can I charge late fees on overdue invoices in Illinois?
Yes — on business-to-business invoices. If your contract or invoice states a late-fee rate, that rate governs (subject to the cap rules below). If nothing was agreed: 5%. Statutory legal rate on written instruments and money wrongfully withheld when no rate is agreed. Statute: 815 ILCS 205/2, 205/4, verified 2026-08-19. Consumer and rent debts follow separate laws.
What is the maximum late fee on a B2B invoice in Illinois?
For a written B2B contract: 9% nominal written-contract ceiling — but business/commercial credit is broadly exempt (any agreed rate). Basis: 815 ILCS 205/4(1)(a),(c). The full cap analysis is on the Invoice (B2B) tab; this covers business-to-business deals only — consumer credit has stricter separate caps.
What interest applies if my contract doesn't mention late fees in Illinois?
The statutory default rate of 5%. Statutory legal rate on written instruments and money wrongfully withheld when no rate is agreed. Statute: 815 ILCS 205/2, 205/4 (verbatim quote on this page, verified 2026-08-19).
Where does this data come from, and when was it verified?
Every invoice-interest figure on this page comes from our 51-jurisdiction dataset: each row researched against the controlling statute or the state's official current-rate page, independently re-checked, and stamped with its own verification date — Illinois's row was last verified 2026-08-19. The operative legal text is quoted verbatim on this page with a link to the official source, the methodology is public, every verification pass is logged in the changelog, and the full dataset is downloadable (CC BY 4.0).
Not legal advice. This page summarizes Illinois's commercial-interest statute for general information, with the verification date shown above — it tells you when we last confirmed the figures, not that they are still current today. Statutes change and courts interpret them; verify the cited statute at the official source, or ask a licensed attorney in your state, before charging a late fee or demanding interest.