A Michigan tax audit is the Department of Treasury’s review of a return you filed (or should have filed) under the state Revenue Act, and under MCL 205.21 the Department generally has four years from the later of the filing deadline or your actual filing date to assess additional tax, interest, or penalties. That window covers individual income tax, corporate income tax, sales and use tax, and most other state-administered taxes. Being audited doesn’t mean Treasury thinks you cheated; many audits close with no change, and some produce refunds. What determines the outcome is how you respond to each notice and whether you use the rights the statute gives you.
When the Four-Year Window Doesn’t Apply
Two situations remove the four-year limit entirely. If you never filed a required return, there is no statute of limitations, and Treasury can go back as far as it wants. If you fraudulently concealed a liability or failed to tell the Department about a change to your federal return, the state gets two additional years from the date it discovers the fraud or the unreported federal adjustment. In both cases, tax, penalties, and interest run from the original due date, not the date Treasury catches up with you.
For audits started after September 30, 2014, Treasury is on its own clock too: it must complete fieldwork and issue a written Preliminary Audit Determination within one year after the statute of limitations would otherwise expire.
Your Rights Once Treasury Contacts You
Michigan’s Taxpayer Bill of Rights, codified in administrative rules, sets several protections that take effect the moment you receive an audit letter.
- You can be represented by anyone you choose: an accountant, attorney, bookkeeper, tax preparer, or anyone else. You do not have to meet the auditor alone, and you do not have to hire a lawyer.
- Auditors have to behave professionally, follow your business hours, and get permission before using your phone or copier.
- The Department is prohibited from using collection quotas during audits. The auditor’s job is to verify the return, not to hit a revenue target.
- Your audit confirmation letter identifies the auditor, audit supervisor, and audit manager by name and phone number, so you know whom to escalate to.
- Treasury maintains a taxpayer advocate office for people who feel they are being treated unfairly. Contact information comes with the confirmation letter.
The Sequence of Notices and Deadlines
Michigan audits follow a statutory sequence, and each step has a deadline that matters. Missing one can forfeit your right to challenge the result.
Letter of Inquiry
Most audits open with a letter of inquiry, which the statute requires to be written in “courteous and non-intimidating” language. It explains why Treasury thinks you may owe more tax and gives you 30 days to respond. Many disputes end here when the taxpayer sends a missing form or documents a legitimate deduction. The Department can skip this step in three situations: you filed a return showing tax due and didn’t pay it, the deficiency came out of an audit of your books, or you’ve already admitted the tax is owed.
Notice of Intent to Assess
If the inquiry doesn’t resolve things, or wasn’t required, Treasury issues a Notice of Intent to Assess. This is the formal document stating how much additional tax the state believes you owe and why. It also lays out your right to an informal conference and the 60-day deadline for requesting one.
Preliminary Audit Determination
After fieldwork, Treasury issues a written Preliminary Audit Determination laying out the proposed adjustments plus tax, penalty, and interest. You can request reconsideration and submit additional documentation. If no reconsideration request is made, the Department has nine months from the Preliminary Audit Determination to issue a Final Assessment.
Final Assessment
The Final Assessment converts the proposed liability into a legal debt. It includes tax, accrued interest, and any penalties. Receiving it starts the clock on your appeal rights, and if you do nothing, collection begins.
What to Pull Together Before You Respond
Once you’re notified, gather records covering every tax year under review, going back the full four years, or longer if Treasury alleges fraud or non-filing. At a minimum, pull copies of all Michigan and federal returns for the audit period along with the supporting schedules and worksheets.
For individuals, the core documents are W-2s, 1099s, bank statements, records for any deductions or credits claimed, and property tax bills if you took the Homestead Property Tax Credit. Farmers claiming the farmland preservation credit should have signed preservation agreements and assessor classifications ready. Businesses need general ledgers, point-of-sale records, sales tax reports, purchase invoices, and complete beginning-of-year and annual inventory records. Treasury can require these in paper, electronic, or digital format.
The single most useful preparation step is reconciling your bank deposits against reported income. Auditors routinely compare total deposits to total revenue, and anything unexplained tends to be treated as unreported income. If deposits exceed what you reported, be ready to show the source: loan proceeds, transfers between your own accounts, gifts, or other non-taxable inflows.
Penalties and Interest Added to the Tax
Penalties and interest stack on top of any additional tax the audit finds, and the amounts move quickly.
For failure to file or pay on time, the penalty is 5% of the unpaid tax for the first two months, plus an additional 5% for each month or partial month the failure continues, capped at 25%. A taxpayer six months late on $10,000 of tax owes a $2,500 penalty on top of the tax.
Treasury can also impose discretionary penalties based on the conduct behind the underpayment. Negligence carries a 10% penalty on the deficiency. Intentional disregard of the tax rules carries 25%. Fraud carries 100%, effectively doubling the tax owed. When more than one applies, only the most severe is assessed.
Interest runs from the original due date of the tax until the balance is paid. The rate is set at one percentage point above the adjusted prime rate and is recalculated twice a year, once based on the six-month period ending March 31 (effective the following July 1) and once based on the period ending September 30 (effective the following January 1). A three-year-old deficiency therefore carries three years of accrued interest before the assessment even lands.
Disputing the Assessment: The Informal Conference
If you disagree with the Notice of Intent to Assess, you have 60 days from the date of the notice to request an informal conference in writing. Your request has to identify the specific amounts you are contesting and explain why. You also have to pay any portion of the liability you are not disputing; you cannot hold back the uncontested amount while fighting the contested part.
Once Treasury receives a valid request, it schedules the conference with at least 20 days’ written notice. A hearing referee, who operates independently from the audit staff, presides. You and the auditor each present evidence and arguments. The referee issues a recommendation, and Treasury makes the final decision. If the decision goes against you, a Final Assessment follows; if it goes in your favor, you may receive a revised bill or a refund.
Requesting the informal conference is not optional if you want to preserve further appeal rights. It is how you satisfy the administrative remedy requirement before going to the Michigan Tax Tribunal.
Appealing to the Michigan Tax Tribunal
If the informal conference doesn’t resolve things, you have 35 days after Treasury’s final decision to file a petition with the Michigan Tax Tribunal, an independent quasi-judicial court separate from the Department of Treasury.
The Tribunal has two tracks. The Small Claims Division runs informally: hearings happen by phone, last about 30 minutes, and parties usually represent themselves without attorneys. There is no formal record, and cases generally take 12 to 18 months from filing to decision. The Entire Tribunal hears larger or more complex cases with formal evidentiary hearings and a complete record. Filing fees for non-property tax appeals start at $250.
One choice is worth thinking through at the start. Small Claims Division decisions are final and cannot be appealed. If you want the option of further review by the Michigan Court of Appeals, file with the Entire Tribunal instead.
What Happens If You Ignore the Final Assessment
Not responding is the costliest mistake a Michigan taxpayer can make. Treasury’s collection powers are broad.
- A tax debt automatically creates a lien against all property you own. The lien attaches from the date the return was originally due and, once recorded, takes priority over most other creditors for seven years, renewable for another seven.
- After a demand letter and 10 days with no response, Treasury can get a warrant and levy your bank accounts, wages, and other property. It can also seize and sell real and personal property found in the state.
- Treasury is required to offset any pending state refunds against outstanding tax debt. This year’s refund goes to last year’s balance first.
- The state can file a civil lawsuit for a judgment, which opens additional collection tools and extends the enforcement timeline.
Interest and penalties keep accruing the whole time. A $5,000 deficiency can grow to $8,000 or more once liens, levies, and additional penalties are added.
If You Haven’t Filed and Haven’t Been Contacted Yet
Michigan’s Voluntary Disclosure Program is the one route that works only before Treasury finds you. It caps the lookback at four years for income taxes and 48 months for sales, use, and withholding taxes, and waives all discretionary and nondiscretionary penalties for the lookback period. You still owe the full tax plus statutory interest, but losing the penalty layer alone can save thousands.
To qualify, you must be a nonfiler with no previous contact from Treasury about the tax in question, no notification of an impending audit, and no current audit or investigation. You agree to register, file going forward, and file returns and worksheets for the lookback period. In exchange, you give up the right to protest or seek a refund for the lookback period on the disclosed issues. The moment Treasury contacts you about the unfiled tax, the program is no longer available.