Michigan calculates child support using the Michigan Child Support Formula (MCSF) — which combines both parents' net incomes and factors in parenting time through a continuous overnight formula. Unlike most states that apply a parenting time reduction only after a specific overnight threshold, Michigan adjusts support incrementally for every overnight a parent has. The current formula is the 2025 MCSF, effective January 1, 2025, which lowered the medical expense threshold and extended the childcare age limit.
Two significant changes took effect January 1, 2025. The ordinary medical expense threshold dropped from $454 to $200 per child per year — parents now absorb the first $200 before shared expense provisions apply. The childcare age limit extended from age 12 to age 13, meaning work-related childcare costs are included through the last day of the month the child turns 13.
How Michigan defines net income and what deductions are allowed, how the MCSF formula combines both incomes, Michigan's unique continuous overnight formula and why it differs from threshold-based states, add-on expenses, deviation factors, and how the Friend of the Court system works.
How Michigan calculates net income
Michigan uses net income — not gross income. The objective under the MCSF is to determine how much money each parent actually has available to contribute to child support after taxes and essential obligations.
Net income starts with income from all sources: wages, salary, bonuses, commissions, self-employment earnings, rental income, interest, dividends, Social Security benefits, disability payments, unemployment compensation, and virtually any other regular financial resource.
- Actual income taxes paid — federal, state, and local
- Court-ordered life insurance premiums (term life only, if ordered by the court)
- Existing child support orders actually being paid for other children
Michigan is careful about what gets deducted. One notable provision: depreciation on real estate, home offices, and personal vehicles that appears on business tax returns generally gets added back into income. The MCSF's logic is that depreciation is a tax deduction, not an actual cash expense — the parent still has those funds available for support purposes.
If a parent is voluntarily unemployed or earning below their capacity, Michigan courts may impute income based on what that parent could reasonably earn given their work history, education, and the local job market.
The proportional income share calculation
Once each parent's net income is determined, the two are combined. Each parent's income percentage of the combined total drives their share of the support obligation. The 2025 MCSF removed a prior limitation that had capped each parent's income share between 10% and 90% — now each parent's actual share of combined income is used directly, however large or small.
Hypothetical example. Actual support amounts depend on the official MCSF formula applied through the state's MiChildSupport calculator. Use pcal.state.mi.us for a precise calculation.
Michigan's formula is more complex than a simple lookup table. The exact amount requires running both parents' net incomes through the official MiChildSupport calculator, which also applies the continuous overnight adjustment automatically. Always verify with a licensed Michigan family law attorney.
Michigan's continuous overnight formula — the key difference
This is what sets Michigan apart from every other state covered in this series. Most states use threshold-based parenting time adjustments — you either clear a specific overnight count (73 nights, 90 nights, 123 nights, 146 nights) and get a reduction, or you don't.
Michigan doesn't work that way. The MCSF uses a continuous formula where every overnight the paying parent has with the child factors into the calculation. There is no minimum threshold. A parent with 50 overnights gets a smaller reduction than one with 100 overnights, who gets a smaller reduction than one with 150 — and each additional night incrementally shifts the obligation.
In states with thresholds, a parent with 89 overnights and one with 91 overnights can have very different support obligations — because one cleared the threshold and one didn't. In Michigan, the difference between 89 and 91 overnights produces a small, proportional difference in the support amount. The formula is smoother and arguably more fair — and it means every overnight in a custody agreement carries real financial weight.
Because parenting time affects support continuously, Michigan parents have a stronger incentive to document and formalize their actual parenting schedule in court orders. If the schedule on paper doesn't match reality, the formula may not reflect what each parent is actually spending on the child day to day.
Add-ons: medical expenses, childcare, and health insurance
The base MCSF obligation is supplemented by three categories of add-on expenses shared proportionally between parents.
Ordinary medical expenses: Under the 2025 MCSF, each parent is responsible for the first $200 per child per year in ordinary medical costs — doctor's visits, over-the-counter medications, routine care. This threshold dropped from $454 under the prior formula. Costs above $200 are shared proportionally.
Work-related childcare: Childcare costs that allow a parent to work or complete their education are added to the formula and shared proportionally. Under the 2025 MCSF, these costs are included through the last day of the month the child turns 13 — extended from age 12 under the prior formula.
Health insurance premiums: The children's share of health insurance premiums is factored into the calculation. If one parent provides coverage, the cost is shared between the parents proportionally based on income.
Deviation from the MCSF
Michigan courts treat the MCSF result as the presumptive correct amount. A deviation is possible but requires specific justification — the existence of a deviation factor doesn't automatically produce a different number; the court still exercises judgment about whether deviation is appropriate.
The MCSF's list of deviation factors is not exhaustive. Common grounds courts may consider include a child's special needs, extraordinary educational expenses, cases where a parent is a minor, and situations where one parent's share of childcare expenses under the formula would exceed 50% of their entire base support obligation. Courts may also consider any other circumstances they find relevant to the child's best interest.
The Friend of the Court
Michigan's Friend of the Court (FOC) is a court agency that plays a larger role in Michigan's child support system than similar agencies in most other states. Every Michigan county has a FOC office. The FOC investigates disputes, makes recommendations to judges on parenting time and support, processes payments, and enforces orders when payments fall behind.
Most Michigan child support payments flow through the State Disbursement Unit rather than directly between parents. The FOC tracks payment history and has enforcement tools including wage garnishment, tax refund interception, license suspension, and contempt proceedings.
If you're navigating divorce finances in Michigan more broadly, our Michigan divorce finances overview covers property division, alimony, and retirement accounts. We also have a guide on how alimony is calculated in Michigan — including the 14 statutory factors and Michigan's fault considerations.
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Common questions about Michigan child support
When does Michigan child support end? Child support in Michigan ends when the child turns 18. If the child is still enrolled in high school at 18, support may continue through graduation — but Michigan law caps this extension at age 19 and a half. Courts may order support beyond 18 for a child with a disability that prevents self-support.
Can Michigan child support be modified? Yes. Either parent may seek a modification through the FOC or directly through the court. Michigan allows a modification when there has been a change in circumstances that would produce a support amount at least 10% different from the current order when the MCSF is applied to current incomes. Either parent can request an administrative review every 36 months.
What if a parent is self-employed? Self-employment income is included. Michigan courts look at business revenue minus ordinary and necessary business expenses. As noted above, depreciation on real estate and personal vehicles typically gets added back into income — this is one of the more nuanced aspects of Michigan's formula and is worth discussing carefully with an attorney if significant business deductions are involved.
What if parents agree to a different amount? Parents may stipulate to a support amount that differs from the MCSF result — but the court must approve it, and the court is required to calculate what the MCSF amount would have been. The judge can approve a deviation from the formula if doing so serves the child's best interest, but the formula number must be disclosed in the record.
Educational purposes only. This article provides general information about how Michigan child support is typically calculated and is not legal or financial advice. Every case is different and outcomes vary significantly based on specific circumstances, judicial discretion, and factors not captured here. Always consult a licensed family law attorney in Michigan for advice specific to your situation.