Commercial Utility Bill Audit in Illinois: Find Billing Errors
Last reviewed: 7/31/2026
By Illinois Commercial Energy editorial team · Reviewed by JakenEnergy commercial energy team
A commercial utility bill audit asks a different question than a pricing review: not is this rate competitive, but is every charge on this bill correct. On complex commercial accounts — multiple meters, demand billing, tax exemptions, transportation status — errors do occur, and they persist until someone checks.
Who this is for
Businesses with commercial or industrial accounts where billing complexity creates room for error: manufacturers with tax exemptions, multi-meter facilities, accounts that changed rate class, and any operation that suspects a charge doesn't look right.
What an audit examines
- Rate class / schedule — is the account on the correct tariff for its usage and demand profile? An account can be left on a schedule that no longer fits.
- Meter data and multipliers — are reads, multipliers, and any CT/PT factors applied correctly, and do interval sums reconcile to billed usage?
- Tax status and exemptions — is an applicable exemption (for example, an Illinois manufacturing exemption) correctly reflected, or is tax being charged that shouldn't be?
- Utility riders and adjustments — do delivery riders and adjustments match the tariff for the account's class?
- Supplier charges — do supply charges match the executed contract (rate, term, pass-throughs, fees)?
Why errors persist on commercial accounts
Billing errors rarely announce themselves. A commercial account is set up once — a rate class assigned, a multiplier configured, an exemption filed or not filed — and then each month's bill reproduces that setup. If the setup was wrong, or if the business changed (added a shift, installed larger equipment, moved into manufacturing that qualifies for an exemption) while the account stayed the same, the bill keeps applying the old assumptions. Nothing on the statement flags the mismatch, because from the utility's side the bill is internally consistent. It takes a deliberate comparison against the applicable tariff and the account's actual operating profile to surface the gap.
Complexity multiplies the room for error. A single-meter account on a simple schedule has few places to go wrong. A facility with multiple meters, current-transformer metering, demand billing, a tax exemption, and a supplier contract has many interacting parts — and an error in any one of them can quietly ride along for a long time.
How an audit reconciles the numbers
The core of an audit is reconciliation: does the bill's own math hold up against the tariff and the meter data? That means confirming the read and any multiplier or CT/PT factor produce the billed usage; checking that billed demand matches what the interval data shows for the peak interval; verifying each delivery rider and adjustment is one the account's class actually carries; and matching supplier line items to the executed contract's rate, term, and pass-throughs. When a figure doesn't reconcile, that gap is the candidate error to investigate — not an assumption of wrongdoing, but a discrepancy that deserves an explanation.
What an audit is not
It is not a promise of a refund or a savings figure. Whether an error exists — and whether it is recoverable — depends on the specific account and the utility's tariff and timeframes. We describe what can be checked and what a confirmed error means, without inventing an outcome.
Audit and review together
The bill review and the audit start from the same document and are complementary: the audit confirms the bill is correct, the review assesses whether the pricing and contract timing are competitive. Running both gives a complete picture before a renewal.
Getting started
Provide one or more recent commercial bills — ideally with a 12-month history and, for larger accounts, interval data and the meter/account inventory. For manufacturers, note any tax exemption you believe should apply; for multi-meter sites, the meter list; and if you have the executed supply contract, include it so supplier charges can be checked against the terms. Bills contain confidential account information; submit them only through the secure request rather than any public channel. An audit describes what can be checked and what a confirmed error would mean — it does not promise a refund, because whether an error exists and whether it is recoverable depends on the specific account and the utility's tariff.
Frequently Asked Questions
QWhat does a utility bill audit check?
Accuracy against the applicable tariff and account setup: whether the account is on the correct rate class, whether meter multipliers and reads are applied correctly, whether applicable tax exemptions (for example a manufacturing exemption) are in place, and whether utility riders and supplier charges match the contract and tariff. The goal is to catch errors, not to shop supply.
QHow is an audit different from a bill review?
An audit is about correctness — is every charge right for this account under the tariff. A review is about pricing and timing — is the supply rate competitive and when does the contract end. An audit can surface recoverable errors; a review informs the renewal decision.
QCan billing errors be recovered?
Sometimes. Where a genuine error is confirmed — a wrong rate class, a misapplied multiplier, a missed exemption — it may be correctable and, depending on the utility's rules and timeframes, adjustable retroactively. Outcomes depend on the specific error and the utility's tariff, and cannot be promised in advance.
QWhat kinds of errors show up most often on commercial bills?
The recurring ones involve setup rather than arithmetic: an account left on a rate class that no longer fits its usage or demand profile, a meter multiplier or CT/PT factor applied incorrectly, a tax exemption that was never filed or dropped off, and supplier charges that don't match the executed contract. These persist quietly because each bill looks like the last one — which is exactly why a deliberate check against the tariff is worthwhile.
QDo I need interval data for an audit?
Not always, but it helps on demand-billed and multi-meter accounts. Interval data lets an audit reconcile metered usage and peak demand back to what was billed, which is how a misapplied multiplier or a demand-calculation error becomes visible. For a simpler single-meter account, recent bills and the tariff may be enough.
QHow far back can an audit look?
An audit can examine whatever billing history you can provide, and a longer run makes a persistent setup error easier to confirm. Whether a confirmed error can be corrected retroactively — and for how long — depends on the utility's tariff and rules, not on the length of history alone. The audit identifies the error; the utility's timeframes govern any adjustment.
Related guides
Sources
- ComEd — Rates & Rules (tariffs)
- Ameren Illinois — Rates and tariffs
- Illinois Commerce Commission — utility tariffs and authority
- Nicor Gas — Rates and tariffs
Next scheduled review: 10/30/2026. Time-sensitive rate, tariff, capacity, and incentive details should be confirmed against the linked primary sources and a current bill.