Illinois Prompt Pay Law: 5 Key Deadlines for Providers
The Illinois prompt pay law sets how fast health plans must pay your claims, and what interest they owe when they do not. This guide helps Illinois therapists and psychiatrists use it. Status is current as of October 17, 2026. This is operational guidance, not legal advice.
1. What the Illinois prompt pay law says
The rule sits in Section 368a of the Illinois Insurance Code (215 ILCS 5/368a), titled “Timely payment for health care services.” The Illinois General Assembly text says claims shall be paid within 30 days after receipt of due written proof of loss. In plain terms, a complete claim should be paid in 30 days. See the Billing Terms Glossary for “clean claim.”
Think of it as a clock. The clock starts when the payer receives a complete claim. If the payer misses the deadline, interest starts to build. Many Illinois practices never ask for that interest, so ask.
2. Who the Illinois prompt pay law covers
The statute names insurers, health maintenance organizations (HMOs), managed care plans, health care plans, preferred provider organizations (PPOs), third-party administrators, independent practice associations and physician-hospital organizations. That covers most commercial plans regulated by the state.
3. Who the Illinois prompt pay law does not cover
The Illinois Department of Insurance (IDOI) says it does not regulate several plan types. Its provider complaint page lists:
- Self-insured employer plans, where the Prompt Pay Law does not apply
- Medicare and Medicare HMOs
- Medicaid and KidCare
- Workers’ compensation
Self-funded plans are usually governed by federal law. Medicaid managed care follows state Medicaid rules and your contract instead. Check each plan’s type on the member’s card or with the payer. Our guide to in-network vs out-of-network billing helps with contract terms.
4. Deadlines and interest under the Illinois prompt pay law
If a payer needs more documents, it must tell the insured, assignee or provider within the same 30-day window, and the clock restarts when the documents arrive, according to an Illinois provider association summary. Late claims earn interest at 9% per year from the 30th day. Interest under one dollar need not be paid, and interest is due within 30 days after the payment.
Keep proof of the submission date. IDOI asks for it with prompt pay complaints, such as an electronic confirmation or a certified mail receipt.
Note that a claim is not “due” if it is incomplete. A missing diagnosis, a wrong member ID or a missing rendering provider can stop the clock. Fix those items fast and keep the date you resubmitted. Corrected claims may restart the payer’s timeline, so check the contract.
5. How to file a prompt pay complaint with the state
Contact the payer first and document each call. Then file with IDOI online or mail the Health Insurance Products Provider Complaint Form. IDOI says complaints must be in writing. Include the ID card copy, the claim form and proof of your attempts to resolve it. IDOI reviews the payer’s response and sends you a written result. It has limited authority over medical necessity and fee disputes. See our State & Regional Billing Guides and insurance companies contact page for payer lines.
| Payer type | Where the rule lives | What to check |
|---|---|---|
| Private insurance | State prompt pay statute and the plan contract | The payment deadline and what the plan calls a clean claim |
| Medicaid | State Medicaid agency and the managed care plan contract | Filing and payment timelines, which vary by state |
| Medicare | CMS and your Medicare Administrative Contractor | Federal claim timing rules, separate from state law |
Practical tips for the Illinois prompt pay law
Log the date you submit every claim and the date it is paid. Set a 30-day reminder for each one. When a payer runs late, send a written inquiry and cite the Illinois prompt pay law. Check each payment for interest on late claims. Review unpaid claims weekly. Make a habit of reading the Illinois prompt pay law section before you escalate, so your letter names the right deadline. Learn more in our practice management tips.
Where MCM South helps
MCM South Medical Billing Service, LLC bills for psychotherapists and psychiatrists in ten states: Georgia (GA), Massachusetts (MA), Connecticut (CT), Texas (TX), Florida (FL), New York (NY), Colorado (CO), Tennessee (TN), North Carolina (NC) and Illinois (IL). We handle claims, denials and follow-up so you can focus on patients. Get a Free Quote or Schedule a Consultation.
Keep learning: Browse the Resources hub and our credentialing page to see how network status affects payment terms.
More from MCM South: Illinois insurance companies contact guide; clean claim glossary entry; timely filing glossary entry; underpayments guide; claim status inquiry guide.
FAQs
How long does an insurer have to pay a claim in Illinois?
The statute says within 30 days after receipt of due written proof of loss, with an insufficiency notice due in the same period.
What interest applies to late claims?
The statute text we reviewed sets 9% per year from the 30th day. Interest under one dollar need not be paid.
Does it apply to self-funded employer plans?
No. IDOI says the Prompt Pay Law does not apply to self-insured employer plans.
Where do I complain about a late-paying insurer?
File with the Illinois Department of Insurance, online or on its provider complaint form, after contacting the payer.
