Illinois Sales Tax for Contractors: Materials, COGS, and Government Jobs

What Illinois Actually Taxes a Construction Contractor On

Contractors Are Consumers, Not Retailers

Most contractors know they are not supposed to charge Illinois sales tax to their customers. Assuming this is a real property job, you are the end consumer of the materials. In that case, you would be the end user for Illinois tax purposes, and the tax obligation would be on you at the time of purchase per 86 Ill. Adm. Code 130.2075.

In practice, if your supplier did collect Illinois tax when you purchased the materials, you are taken care of. The same applies if you accrued and paid tax on your materials that became real property. If neither of those is true, and the audit notification shows up at your business, then you would owe tax on the materials at cost, plus penalty and interest.

Knowing the auditor's playbook is critical to understanding their thinking and what they are looking for. IDOR's Sales Tax Audit Manual, the auditor's rulebook, describes four occasions when tax is applicable: delivery of materials to the job site, charge for a job in your job cost accounting system, withdrawal of materials from general inventory for a project, or the month you pay your supplier on a receipts basis. Auditors will look at all four. Essentially, this means the tax applies when the material is "used," not when the project is completed. If your controller reconciles sales tax at the completion of the project, chances are it has been three months since the taxable event occurred.

Buying supplies from an out-of-state supplier who didn't charge Illinois tax? You have to self-assess and pay Illinois Use Tax under 35 ILCS 105. You may credit the tax that you legally paid to another state, up to the Illinois tax rate. This situation with contractor audits is almost always a surprise and can result in significant tax out of your pocket.

The Real Property vs. TPP Classification Problem

There is another situation where both sides of the transaction have liability issues.

A contractor treats a job like real property. They pay tax on materials used and charge the customer nothing. An IDOR audit finds that the work was a sale of tangible personal property (TPP). In this case, you should NOT have paid tax on the materials used. However, you SHOULD have charged the customer tax on the materials (and sometimes the labor). In this case, you paid tax on the materials when you should not have, and you did not charge the customer the tax when you should have. If it is tangible personal property, then you can be on the hook for the differential in tax.

My rule: consider your work to be TPP along with the burden on you unless you find a statute, an IDOR publication, or a ruling that states that your work is considered installed real property. For example, if you sell and install an A/C unit that is part of a building, look it up. In most states, there is likely a publication or guidance that says HVAC installs are real property and tax is due on the material cost to the contractor. Follow whatever that publication states. If there is nothing specific, assume the higher tax scenario, or you can choose to take on that risk.

Selling TPP uninstalled is more straightforward. In that case, apply the normal rules to TPP and charge tax on the sale. The determination of real property versus tangible personal property only matters when the contract includes the installation.

The Resale Certificate Trap

A contractor learns their Illinois registration number and also learns about resale certificates. Because the logic explains itself, a contractor begins to use them on every single purchase of a material. Why should I pay tax on materials if I'm not selling the materials to my client?

The answer resides in 86 Ill. Adm. Code 130.2075(b)(3). A resale certificate is legitimate when a contractor, in the course of their own business, sells personal property at retail and is, in fact, uncertain at the time of the purchase if the specific item will be incorporated in the work or sold. If the material is incorporated into every single project, the certificate does not apply. Once the materials are incorporated into real property in accordance with 86 Ill. Adm. Code 130.2075(b)(3), Special Use or ROT Tax is due from the contractor as if the supplier has been paid by the contractor.

The certificate changed the date of the determination, but it did not eliminate the obligation.

As stated in IDOR's Audit Manual, "audits of construction contractors are completed by examining purchases in a manner where all material costs are accounted for." Each and every purchase in the ledger, each and every resale certificate claim, each and every job-cost account. If the resale certificate was used on purchased materials shown in the records with no corresponding Special Use Tax returns, the gap would become the assessment. One detail most controllers do not know: IDOR imposes tax at the contractor's local Special Use Tax rate, not the supplier's tax rate. A contractor in Springfield who purchased materials from a supplier in Chicago is obligated to pay the materials tax in Springfield at the cost of the materials.

There are no exceptions to the Illinois law where a subcontractor can take a resale certificate from a prime contractor for materials provided and converted to real property. The language in 86 Ill. Adm. Code 140.108(a)(3) is absolute. Each party is liable for the tax on the purchase of the materials and the tax on its own installation, at its local jurisdiction and the cost price. Whether the contractor is union or non-union makes no difference. I have seen time and time again, that IDOR is solely concerned with whether the subcontractor provided and incorporated the materials into the project. This is one of the issues that IDOR focuses on during contractor audits.

When this issue comes up during your ledger review, you have the opportunity to utilize the voluntary disclosure program before IDOR initiates an audit. When IDOR contacts you, this opportunity closes.

Government Contracts Are Not a Blanket Exemption

I call these "gotcha" moments. A lot of contractors assume that materials used for government projects are exempt. Contractors are correct under 86 Ill. Adm. Code 130.2075(d) as long as all procedures were followed for every single invoice for every single job. I have rarely, if ever, seen this happen.

The materials exemption applies to real property that the government owns. This exemption does not apply to anything a contractor purchases for a government job. Taxable sales include fuel for forms, scaffolding, and even consumables, even if there is no title transfer. The IDOR Audit Manual, Section 13.8.8, states that sales of these things "are taxable sales regardless of who the contractor's customers may be." There is no title transfer to a governmental entity? The exemption does not apply, absent following the rule meticulously.

The procedure for claiming an exemption under 86 Ill. Adm. Code 130.2075(d) and 130.2076 requires specific documentation for each government job. For every job, the contractor must provide invoices containing the name of the exempt job. The contractor must provide the governmental entity's exemption number and must certify that the purchases are for incorporation into real property under contract with that governmental entity. In addition, the contractor must provide the IDOR registration number of the governmental entity for public improvements that are transferred to a local government. This is the item that catches contractors most often. One missing item means the entire exemption for that job does not apply.

In short, the exemption on government contracts requires: (1) the governmental entity must obtain title to the materials, and (2) the contract must specify the materials and supplies will transfer to the government. A general title-transfer clause in the contract satisfies this requirement. Without that language in the contract, consumables are considered taxable. Review the latest versions of your government contract templates. For contracts without that clause, those purchases are a cost to your organization. Although it doesn't feel right, you are likely better off paying tax on the material purchases to avoid exposure or get professional help to ensure the rules are strictly followed.

Getting Ahead of an IDOR Review

IDOR auditors don't run spot checks. This is a completeness exercise: every material cost must be accounted for and either shown as taxed or assessed as a liability. The auditor works for the State of Illinois. Their job is to assess additional tax, and understanding that as a structural reality, not a personal judgment about any individual auditor, is the most important thing I can tell you going in. The audit sampling methodology IDOR uses means a finding in one period gets projected across the full audit window.

If your ledger review surfaces resale certificate use on incorporated materials, or incomplete government contract documentation, act before IDOR contacts you. A voluntary disclosure lets you address the liability without the full penalty exposure. If you've already received a Notice of Tax Liability, you have 60 days from the date on that notice to request Informal Conference Board review using Form PIO-58. The clock runs from the notice date. Not the date you opened it.

If your controller's ledger looks like what I described, don't wait. Reach out online or call (866) 458-7966 to speak with a Sales Tax Helper attorney. Our Illinois sales tax audit defense starts with a free consultation.

FAQ

Are Illinois construction contractors required to pay sales tax on materials purchased?

Illinois construction contractors are required to pay sales tax on materials purchased, and the tax obligation is triggered when materials are purchased, not when the construction project is completed. Illinois construction contractors are considered material consumers, and not material retailers, when they incorporate materials in real property. Tax is charged at the time of purchase and is remitted to the supplier at the time of purchase or is self-assessed as Use Tax if the supplier did not collect the tax. There is no exemption for building for a private client.

Can I use resale certificates for construction materials in Illinois?

A resale certificate may be used for construction materials in Illinois only in rare instances. Your company must be engaged in the retail sale of tangible personal property, and you must be uncertain at the time of purchase, whether the property will be resold or incorporated. Once materials are incorporated into real property, ROT or Use Tax is due. Use of a resale certificate in order to avoid payment of sales tax on costs of goods sold (COGS) will result in an assessment of taxes by the Illinois Department of Revenue (IDOR), on audit.

Do government contracts exempt Illinois sales tax on supplies?

Materials integrated into real property owned by a government agency are exempt, but require documentation. Exemption documentation for each job must include the exempt job named on all invoices, the government agency's exemption number, and, where the improvement is for the public, the active IDOR registration number for the government agency. Exemption will be denied for any job without this documentation. Tools, fuel, and consumables that are not integrated into real property are taxable to the customer, regardless of their identity.

Does an Illinois subcontractor have an obligation to collect sales tax if the prime contractor has a resale certificate?

Yes. According to 86 Ill. Adm. Code 140.108(a)(3), a prime contractor's resale certificate does not protect a subcontractor from the tax obligation on supplies the subcontractor furnishes and integrates into real property. Each party is responsible for tax on the supplies they incorporate and for tax on the cost at the local tax rate of supplies that were provided to them. The prime contractor's resale certificate provides no protection to the subcontractor.

Why would an Illinois Department of Revenue (IDOR) audit a construction contractor?

The IDOR audits construction contractors for several reasons, including: the failure to file a Return of Taxes Owed (ROT) for resale certificate purchases of material, a failure to file Use Tax, significant material purchasing activity outside Illinois, and the use of government contract exemptions without providing appropriate documentation. IDOR auditors look at each material purchase to ensure the tax obligation is satisfied. A pattern of resale certificate use to purchase material with no tax remittance is an audit signal.

If IDOR finds untaxed purchases, what will happen during a contractor audit?

IDOR assesses ROT or Use Tax on cost price for all purchases in the audit period. IDOR may estimate the tax assessed for the entire audit period for a particular purchase based on its sampling methodology. Penalties and interest accrue from the original due date. Once you receive a Notice of Tax Liability, you have 60 days from the date(s) on that notice to request Informal Conference Board review by completing Form PIO-58.

Can a contractor step forward before an audit and admit to past liability?

Yes, this is possible. Contractors are able to report and pay tax on prior period liability with less penalties, compared to what IDOR would assess in the course of an audit. IDOR contact regarding specific liability or the initiation of an audit negates a contractor's ability to utilize voluntary disclosure. The terms prior to contact by IDOR are much more favorable than what is available afterward.

How do I distinguish between real property and tangible personal property for Illinois sales tax?

To begin, we look to the state for something more specific, like a statute, IDOR publication, or a ruling pertaining to your particular kind of work. In the absence of that document calling your work installed real property, then leave it as TPP plus installation. It's more work, but it's safer. Contractors usually end up with exposure on both sides: the tax on material going in and the failure to collect from the customer going out. The safest practice would be to contact a sales tax attorney before you price a job.

About the Author

Gerald J. "Jerry" Donnini II is a sales tax attorney and the founder of Sales Tax Helper, a national platform that helps businesses find, fix, and prevent sales tax exposure before it becomes a problem. Over a 15-year career, he has represented businesses in more than 5,000 sales tax audits, appeals, and disputes across 40+ states. He holds an LLM in Taxation from New York University, is co-author of a CCH treatise on state sales and use tax, and serves as an adjunct law professor. Jerry has saved businesses more than $500 million in sales tax assessments. His framework, Find It. Fix It. Defend It., guides businesses from initial nexus diagnosis through voluntary disclosure and, when necessary, full audit defense.