The Illinois Government Invoice Checklist: What Actually Gets an Invoice Rejected

Most advice about government invoicing is written for federal contractors and then applied to Illinois, where it is wrong in a specific and expensive way. Illinois has two payment regimes, and they treat the invoice document itself in opposite ways.

The State of Illinois defines what an invoice must contain, by statute and by rule. Illinois local governments do not. Read the whole of the Local Government Prompt Payment Act (50 ILCS 505) and you will find no definitions section, no "proper bill," and no list of required fields — Section 3 refers only to "a bill from a vendor or contractor for goods or services furnished."

That single structural difference drives everything below. Against the State, your invoice is measured against a published standard. Against a city, county, township or school district, it is measured against a purchase order.

Part 1 — Invoicing the State of Illinois

The three defects that make a bill improper

The State Prompt Payment Act (30 ILCS 540/1) defines a proper bill as one that "includes the information necessary for processing the payment as may be specified by a State agency and in rules adopted in accordance with this Act." The rules are 74 Ill. Adm. Code Part 900, and Section 900.70(a) is the closest thing Illinois has to a statewide invoice checklist. A bill is not a proper bill if it:

"1) lacks sufficient and/or correct information required by the agency to process the bill; 2) lacks the Vendor's taxpayer identification number or a completed Internal Revenue Service Form W-9 or Form 147C ... or 3) is directed to an address or person other than the one designated in written instructions from the State."

Defect 3 is the one people do not expect. Sending a correct invoice to the wrong person at the right agency makes it an improper bill.

Section 900.20 adds that "Proper Bill" is defined by Part 900, by the Comptroller's Statewide Accounting Management System (SAMS) manual, or as otherwise specified by the State agency responsible for payment. There is no single form. Ask the agency, in writing, what it requires — and keep that written instruction, because Section 900.70(a)(3) makes it the standard you are held to.

The subcontractor line most vendors have never added

Since 1 July 2021, a proper bill must also include "the names of all subcontractors or subconsultants to be paid from the bill or invoice and the amounts due to each of them, if any." This is on the face of 30 ILCS 540/1. If you use subs and your invoice does not name them and their amounts, it is arguably not a proper bill — and the clock has not started.

There is no equivalent requirement anywhere in the Local Government Prompt Payment Act.

The rejection that costs the most — and the one that doesn't

This is the most expensive rule in Illinois state invoicing, and it turns on when the rejection happens. 74 Ill. Adm. Code 900.70(b):

"An agency shall approve Proper Bills or deny bills with defects, in whole or in part, within 30 days after receipt. Vendor bills denied during this 30 day period shall be assigned a new Date of Receipt when a corresponding Proper Bill is subsequently received."

Read those four words carefully. A bill denied inside the 30-day window does not resume — it restarts, and your 90-day interest clock under 30 ILCS 540/3-2(1.05) begins again from the day the corrected bill lands. A missing W-9 caught on day 28 can cost four months.

But the restart is limited to that window, and vendors give up clocks they have not actually lost. Under 900.70(d) a bill approved after the 30-day window still accrues interest from 90 days after receipt of the original proper bill; under 900.70(e) a bill denied after that window and later approved as originally submitted likewise keeps its original receipt date. If an agency sits on your invoice for two months and then queries it, do not assume the clock went back to zero.

And the notice telling you may not be written. Section 900.70(c) provides that the notification "may be verbal or in writing, as the agency may determine is appropriate." If someone calls to say your invoice is defective, that call is the notice. Write it down, confirm it by email, and keep the reply.

The statute does put a duty on the agency's side: under 30 ILCS 540/3-2(1.1), the notice "shall identify the defect and any additional information necessary to correct the defect," and for construction-related bills it must come within 30 days of first submission.

Before you can invoice at all

Registration and invoicing are separate systems, and confusing them wastes weeks.

• BidBuy is the State's bid system — solicitations and awards. It is not where invoices go.
• The Illinois Procurement Gateway (IPG) is where disclosure forms live. Registering in IPG automatically creates a BidBuy account; allow 24–48 hours. Neither costs anything.
• An IDHR eligibility number is required of every entity wishing to do business with the State, obtained by filing the Employer Report Form (PC-1) with the Illinois Department of Human Rights.
• State Board of Elections registration is required where aggregate bids, proposals or contracts exceed $50,000 annually across all State agencies and universities.

Full requirements are published at Pathway to Procurement.

Track the payment yourself

The Illinois Office of Comptroller's vendor services are underused and free:

EVR requires authorized direct deposit — vendors "must have authorized Direct Deposit in order to register for this system." If you are still taking paper warrants, you cannot see the detailed remittance data.

Part 2 — Invoicing an Illinois city, county, township or school district

There is no statewide statutory invoice format. Every field requirement you will ever meet comes from a local ordinance, a purchasing policy, or the purchase order's own terms. Below are real published examples — treat them as the shape of the problem, not as a universal rule.

Chicago asks for a number you cannot produce

Under Centralized Invoice Processing, a Chicago invoice needs the standard fields plus a PO Number, a Release Number where applicable, the name of the ordering department, your contact's name and phone at that department, and a Receipt Number. The City states in capitals that a missing field "WILL delay payment."

The Receipt Number is generated by the ordering department after delivery, in the City's accounting system, and passed to you — by whatever channel that department prefers, since the Comptroller "left it to each department's discretion." You cannot create it. If it has not arrived within 5 business days of delivery, the CIP FAQ instructs you to submit anyway with "TBD – Department" in the Receipt Number field.

Three further Chicago specifics: CIP eligibility is per contract, checked against a list updated monthly — if your contract is not on it, invoices go to the ordering department instead. "Sold To" stays the ordering department's address while only "Bill To" changes to the Comptroller. And do not send duplicates to any department, or Subcontractor Payment Certification forms to CIP.

Use the address on the current CIP page — Office of the City Comptroller, 121 N. LaSalle St., Room 700, Chicago, IL 60602, or INVOICES@cityofchicago.org with INVOICE in the subject line. The CIP Vendor FAQ still shows an older 33 N. LaSalle St. address; it is stale, and it is the kind of detail that quietly misroutes an invoice for a month.

What other Illinois bodies publish

• City of Decatur: every invoice must carry a PO number, and invoices should be "exact as to the quantity, size, grade, description, unit, and total price stated on the purchase order." The mandatory/advisory split is the City's own wording; it states no rejection consequence for line-item variance. No payment before receipt and acceptance. Net 30 thereafter.
• Village of Schaumburg: publishes a literal checklist covering invoices and packing slips — PO numbers, clear quantities, item descriptions, units of measure, contract name and phone. No partial payments unless negotiated.
• Village of Mount Prospect: approves accounts payable twice monthly, average payment 21 days from receipt. The purchase order is the contract, and the Village "will not accept contracts drafted or issued by the vendor."
• Lake County: invoices in duplicate; the PO number on "all invoices, boxes, packages, shipping documents and correspondence."

Sales tax is an invoice problem, not an accounting problem

Under 86 Ill. Adm. Code 130.2080, since 1 January 2015 a sale to a governmental body is exempt only if the body has an active exemption identification number ("E-number") and provides it to you — and only sales "invoiced directly to and paid by" that body are exempt. If an employee pays with a card in their own name, tax is due even if they hand you a valid E-number.

Section 130.2081 puts the recordkeeping on you: keep the Department's letter issuing the E-number, check its expiration, record the active E-number at the time of sale on the bill of sale or purchase order, and note the form of payment. Some bodies publish theirs (Mount Prospect's is E9998-1475); Decatur furnishes it on request; Lake County prints it on the reverse of the PO and treats the PO itself as the exemption certificate.

Two traps worth knowing

No appropriation, no payment. Under 65 ILCS 5/8-1-7, and subject to the exceptions stated in that section, no municipal contract may be made and no expense incurred "unless an appropriation has been previously made," and anything done in violation "shall be null and void as to the municipality, and no money belonging thereto shall be paid on account thereof." The section does carry carve-outs — spending against the prior year's appropriations pending passage of the annual ordinance, certain professional services on a two-thirds vote, and an exemption for municipalities operating under special charters — so check it rather than treating the rule as absolute. It is still the real reason a PO number matters more than a signature at the local level.

Certified payroll is a contract gate, not a statutory one. The Prevailing Wage Act (820 ILCS 130/5) requires filing by the 15th for the preceding month — but nothing in Section 5 conditions a public body's payment on it. The Act's own sanctions are separate and serious: civil penalties payable to IDOL under Section 5(d), and under Section 11a an automatic four-year debarment from public works on conviction under Section 5 or 6. Not a payment gate; a much larger problem than one. Local contracts do: Lake County makes submission "required prior to the issuance of payment," Schaumburg requires certified payroll and waivers with the invoice, and Decatur requires weekly certified copies for prime and subs before invoices are paid. Meeting the statute is not the same as meeting the contract.

Where GoVendor fits

GoVendor works with Illinois government vendors on getting invoices submitted correctly and tracking where they sit, which is upstream of everything above — a defective invoice does not start a clock, and a rejected one under 74 Ill. Adm. Code 900.70(b) starts a new one. The requirements on this page are the law and the published policy of the bodies named; they apply whoever you work with, and nothing here describes a partnership with, or endorsement by, the State of Illinois or any local body mentioned.

Sources

• State Prompt Payment Act, 30 ILCS 540 — Illinois General Assembly
• 74 Ill. Adm. Code Part 900 — Prompt Payment rules (900.20, 900.70)
• Local Government Prompt Payment Act, 50 ILCS 505
• City of Chicago — Centralized Invoice Processing and the CIP Vendor FAQ (PDF)
• Illinois Office of Comptroller — Vendor Services
• Pathway to Procurement — Requirements
• 86 Ill. Adm. Code 130.2080 and 130.2081 — exempt-entity sales
• 65 ILCS 5/8-1-7 — municipal appropriation requirement
• 820 ILCS 130/5 — certified payroll
• Published purchasing terms: Decatur, Schaumburg, Mount Prospect, Lake County

Statutes, rules and municipal pages read on 6 August 2026. The local examples are the published policies of those specific bodies and do not describe any other jurisdiction — always check the purchase order in front of you. General information, not legal advice.