How Massachusetts Calculates Child Support
Massachusetts uses the Income Shares model for child support. The governing authority is the Massachusetts Child Support Guidelines, issued by the Chief Justice of the Trial Court under Massachusetts General Laws Chapter 208, Section 28. The guidelines were most recently updated in 2021 and apply to all child support proceedings in the Commonwealth regardless of whether the parents were married.
Massachusetts combines both parents' gross weekly income to determine the total child support obligation, then splits that obligation proportionally by income. Note that Massachusetts works in weekly income figures internally. The calculator converts to monthly automatically, but the underlying formula uses weekly amounts. The parent with less parenting time pays their share to the parent with more parenting time.
The Massachusetts Child Support Formula
Massachusetts follows four steps.
Step one is determining each parent's gross weekly income. Step two is adding both gross weekly incomes together to produce the combined gross weekly income. Step three is finding the Basic Support Obligation from Massachusetts's schedule using the combined weekly income and number of children. Step four is calculating each parent's income share percentage and applying it to the obligation.
A practical example using weekly figures: Parent A earns $1,150 per week. Parent B earns $575 per week. Combined weekly income is $1,725. Parent A's income share is 66.7 percent. If Massachusetts's schedule sets the Basic Support Obligation at $350 per week for two children at $1,725 combined weekly income, Parent A's base obligation is $233 per week, approximately $1,009 per month.
Massachusetts's guidelines apply to combined gross income up to approximately $400,000 per year. Above that threshold, courts have discretion to set support above the maximum schedule amount based on the children's needs and each parent's resources.
What Counts as Income in Massachusetts
Massachusetts uses a broad income definition. Courts include wages, salaries, overtime, commissions, bonuses, tips, self-employment income, rental income, pension and retirement distributions, Social Security benefits, SSDI payments, unemployment compensation, workers' compensation, and income from any other regular source.
Massachusetts courts can impute income to a parent who is voluntarily unemployed or underemployed. Courts evaluate the parent's work history, education, skills, and the local job market when determining an appropriate imputed income level. A parent who chooses to earn less than their capacity allows cannot reduce their child support obligation by doing so.
Massachusetts also allows deductions from gross income for certain items before combining incomes: existing court-ordered child support being paid for children from other relationships, certain documented childcare costs for other children living in the home, and, in some cases, health insurance premiums the parent pays for themselves. These adjustments reduce the adjusted gross weekly income used in the formula.
Step-by-Step: How to Use This Calculator
Step 1. Convert your income to gross weekly. Divide your annual salary by 52. If you are paid hourly, multiply your hourly rate by your average weekly hours. Include all income sources. Massachusetts works in weekly income figures, so this conversion is the starting point for an accurate result.
Step 2. Subtract any applicable deductions from gross weekly income. If you are paying court-ordered child support for children from another relationship, subtract that weekly amount. If you pay health insurance for yourself, that premium may also be deductible. The result is your adjusted gross weekly income.
Step 3. Estimate the other parent's adjusted gross weekly income using the same method.
Step 4. Enter the number of children covered by this order.
Step 5. Enter your parenting time percentage. Count actual overnights per year and divide by 365. Massachusetts applies a parenting time credit when the paying parent has more than approximately one-third of the overnights per year, roughly more than 121 overnights. At one-third and above, the credit applies and grows as parenting time increases toward 50 percent.
Step 6. Add healthcare costs. Enter the monthly or weekly cost of the children's health insurance premium. Massachusetts adds healthcare costs as a separate line item and allocates them proportionally.
Step 7. Add childcare costs. Enter weekly or monthly work-related childcare expenses that allow either parent to work or attend school.
Step 8. Review the weekly and monthly breakdowns in the results before accepting the final number.
Parenting Time Adjustments in Massachusetts
Massachusetts applies a parenting time credit when the paying parent has more than approximately one-third of the overnights per year. Below that threshold, roughly 121 nights, the standard formula applies with no reduction.
At one-third of overnights and above, the Massachusetts guidelines reduce the paying parent's obligation to reflect the direct costs they bear during their parenting time. The credit grows as overnights increase toward 50 percent. At near-equal parenting time, both parents' obligations are considered and the higher earner pays the net difference to the lower earner.
Massachusetts also has a specific provision for situations where each parent has primary physical custody of at least one child, a split custody arrangement. In those cases, the obligations are calculated in both directions and offset against each other.
Equal parenting time does not automatically produce zero child support in Massachusetts. When one parent earns significantly more than the other, a net payment still flows from the higher earner to the lower earner even at exactly equal custody time.
Add-On Expenses in Massachusetts
Massachusetts adds healthcare premiums and work-related childcare costs to the base obligation. Both are allocated proportionally by income share. Massachusetts is specific about childcare: only work-related childcare costs, expenses that allow a parent to maintain employment or attend job training or school, are included. Childcare for other purposes does not qualify.
Extraordinary medical expenses, unreimbursed costs that exceed a threshold amount per year, may also be split proportionally between the parents through the court order.
Reading Your Results
The results display shows each parent's adjusted gross weekly income, the combined weekly income, the Basic Support Obligation from Massachusetts's schedule, each parent's income share, the parenting time credit if applicable, add-on allocations, and the final weekly and monthly obligation.
Confirm that your income entry is in gross weekly terms and that any applicable deductions for prior support obligations or self-insurance premiums have been applied correctly. The most common input error in Massachusetts is entering monthly gross income without converting to weekly, which produces a significantly lower estimate than what the guidelines would actually show.
After You Get Your Estimate
Massachusetts courts follow the 2021 guidelines in all standard cases. Deviation is allowed when a judge makes a written finding that applying the guidelines would be unjust or inappropriate. Grounds for deviation include a child's extraordinary medical or educational needs, a parent's extraordinary financial obligations, significant travel costs for parenting time, or a situation where the combined income is so high or low that the schedule produces an unreasonable result.
Modification in Massachusetts requires a showing of a material and substantial change in circumstances. A change of 20 percent or more in the calculated obligation is a commonly referenced threshold, though Massachusetts courts evaluate each modification on its specific facts. Income changes, shifts in parenting time past or below the one-third threshold, changes in healthcare costs, and changes in the children's needs are the most common grounds for filing.
If your parenting time has increased and you are now at or above the one-third threshold when you were previously below it, you may be entitled to the parenting time credit for the first time. That change alone can meaningfully reduce your monthly obligation and is worth pursuing through a modification.
Reach out to a licensed Massachusetts family law attorney to review your specific numbers. Many offer a free consultation for child support cases.