Michigan Post Judgment Interest Rate: How to Calculate What You're Owed

That small claims judgment you won doesn't just sit at the original dollar amount while the debtor takes months or years to pay. Michigan law adds post-judgment interest to the balance, and understanding how to calculate it correctly is essential when you fill out garnishment forms or demand payment.

How Michigan Sets the Post-Judgment Interest Rate

The governing statute is MCL 600.6013. For most small claims judgments — which are not based on a written contract with a stated interest rate — subsection (8) controls. The rate adjusts every six months on January 1 and July 1, and it equals the average interest rate paid at auctions of five-year United States Treasury notes during the six months preceding July 1 or January 1, plus one percentage point.

The Michigan State Treasurer publishes the applicable rate each cycle. You need the rate that was in effect on the date your complaint was filed, then track any rate changes through the life of the judgment.

For judgments based on a written contract that specifies an interest rate — a promissory note or a loan agreement with explicit terms — the contract rate applies instead of the statutory formula, provided it's legal under Michigan usury law.

When Interest Starts Accruing

Interest doesn't begin when the judge signs your judgment. Under MCL 600.6013, it accrues from the date you filed your original affidavit and claim (Form DC 84) with the district court. That means the debtor owes interest for the entire period between your filing date and the date the judgment is paid in full, including the time spent waiting for trial and the 21-day post-judgment stay.

How to Calculate the Amount

Here's the arithmetic for an illustrative 121-day segment at a hypothetical, unchanged 6% annual rate:

1. Start with your principal judgment amount (say $4,500)
2. Identify the filing date and the current date
3. Count the number of days between them
4. Multiply: $4,500 × 0.06 × (days ÷ 365)

For a judgment filed on March 1, 2026 and calculated as of June 30, 2026 (121 days), that's $4,500 × 0.06 × (121 ÷ 365) = $89.51 in accrued interest.

If the rate changed mid-period (crossing a January 1 or July 1 boundary), calculate each segment at its applicable rate and account for the statutory annual compounding.

Where the Interest Rate Matters Most

You need this number in two places. First, when you complete the sworn balance on Item 2 of any garnishment writ (Forms MC 12 or MC 13), you must include accrued interest in the total balance claimed. Understating the amount means you legally forfeit the difference. Second, when you send a voluntary payment demand letter, the stated balance should reflect principal plus accrued interest plus any recoverable court costs.

Every payment you receive gets applied in a specific order: first to accrued costs, then to accrued interest, and finally to principal. This means the principal balance — which generates future interest — decreases only after costs and interest are covered.

Tracking Interest Over the Life of the Judgment

Michigan small claims judgments are enforceable for 10 years under MCL 600.5809(3), renewable for another 10. Over that span, interest compounds annually. The statutory rate adjusts every January 1 and July 1 based on the five-year U.S. Treasury note rate plus one percentage point, so a 10-year total depends on each applicable rate and any payments.

Keeping a running ledger that logs every rate change, every payment received, and every enforcement cost added to the balance is the only reliable way to state an accurate sworn balance when you file writs. Courts reject garnishment requests when the math doesn't add up.

If you need a structured system for tracking the full balance — principal, interest, costs, and credits — the Michigan Judgment Collection Roadmap walks through each calculation step with a ready-to-use ledger.

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