The Worksheet’s credit for equal parenting time falls from 77.6 percent to 6.9 percent as the income gap widens, with no measure of time anywhere in the calculation
The worked example below is my own child support order: three children, equal parenting time,
my income and my children's mother's income entered as the Worksheet requires. I disclose it
because a reader should be able to check whether the arithmetic changes when the numbers are real,
not hypothetical. The model that produced every figure on this page is
model/box1_fix.py, checked against
model/worksheet.py and against the form's own
official calculation scripts in
model/runs/official-xfa-vs-model-2026-09-05.txt.
Verified against the form's own calculation scripts
Box 1’s credit for equal parenting time equals the payor’s own Line 6e, and Line 6e has no time in it
Massachusetts’s Worksheet form (CJ-D 304) offers two relevant boxes: Box 2, where one parent has the children the great majority of the time, and Box 1, where the parents share time equally. Both boxes compute the same total support amount at Line 4c ($1,240.73 a week at the worked example: three children, a payor at $201,000 a year, the other parent at $570 a week), then divide it between the parents by their shares of combined income. Line 5b assigns the payor 87.68 percent of that amount, $1,087.90 a week; that figure is the order Box 2 would produce for the same family.
Box 1 subtracts a credit at Line 6g, and that credit is exactly the payor’s own Line 6e: $75.17 a week, capped there because his own income share (4.0 percent of his column’s entitlement) is below 10 percent. $75.17 out of $1,087.90 is 6.9 percent. Nothing in Lines 4c through 6g asks how many overnights either parent actually has.
$75 of $1,088 the equal-parenting credit at the worked example against the order Box 2 would produce for the same family: 6.9 percent, and no line in the calculation measures time
The credit tracks the income gap, not the calendar, and runs backward as the gap widens
Holding the payor’s income and the three children fixed and moving only the other parent’s income shows the same equal-parenting arrangement priced very differently depending on how far apart the two incomes are:
| Other parent's weekly gross | Payor's share of combined income | Box 1 order | Credit against Box 2 |
|---|---|---|---|
| $2,500 | 60.8% | $340 | 64.5% |
| $1,800 | 68.4% | $536 | 46.2% |
| $1,200 | 76.6% | $826 | 20.5% |
| $900 | 81.5% | $920 | 13.3% |
| $700 | 85.1% | $977 | 9.2% |
| $570 (worked example) | 87.7% | $1,013 | 6.9% |
| $400 | 91.2% | $1,075 | 2.6% |
| $250 | 94.6% | $1,103 | 1.3% |
The wider the gap between the two incomes, the smaller the equal-parenting credit: from 64.5 percent of the Box 2 order at a 60.8 percent income share down to 1.3 percent at a 94.6 percent share. At the worked example, an 87.7 percent income share, the credit has already fallen to 6.9 percent.
The Worksheet's credit for equal parenting time collapses as the income gap widens; a cross-credit narrows without collapsing.
The reduction in the order for equal time, against the one-third-time order, falls from about 75 percent at a 57 percent payor income share to 7 percent at 88 percent and 1 percent at 96 percent, because no parenting-time quantity enters any line.
Variant A, applying Line 6e once, lifts the curve; Variant B, the standard cross-credit at a 1.5 duplication factor used by 23 states, stops it collapsing.
Source: model/box1_fix.py · model/charts/fig3_credit.py ·
data (CSV) ·
printed run
Even the fix other states use does not put the calendar into the calculation
The same clip that produces the 6.9 percent credit could be applied differently. Removing it once, so the payor’s own entitlement is not capped a second time (Variant A), raises the order’s reduction to 14.0 percent, an order of $935.06. Applying the standard cross-credit design used by 23 states, at a 1.5 duplication factor (Variant B), raises the reduction to 35.5 percent, an order of $701.30, a 30.8 percent drop from the current $1,012.73. Neither variant adds a term for how much time either parent actually has the children: both change how the income-share gap is priced, not what is being priced.
Priced as overnights, equal time comes out to a third of the calendar under one factor and just under half under another
Massachusetts’s own commentary and the guidelines contain no number for how much of the shared-care cost is duplicated between two households. Other states’ cross-credit formulas do, which makes it possible to solve the Box 1 arithmetic backward. Asking what overnight share, run through a standard cross-credit, would reproduce the actual $1,012.73 order answers how much parenting time Massachusetts is effectively pricing equal custody at. The answer depends entirely on which duplication factor is used, so the factor must always be stated beside the number.
33.3% at factor 1.5 · 46.9% at factor 2.0 the overnight share the Box 1 order at the worked example implies under a standard cross-credit. Never quote one of these numbers without its factor
At the 1.5 duplication factor (the figure Indiana’s Child Support Guideline 6 Commentary uses to quantify equal-parenting duplication), the Box 1 order at the worked example implies an overnight share of 33.3 percent. At the 2.0 factor implied by Box 1’s own uncapped arithmetic (both parents’ columns carry every child at the full schedule amount), it implies 46.9 percent. Neither reaches the 50 percent the parent in the worked example actually has.
At the worked example, equal parenting time is priced as a third of overnights at factor 1.5, and 47 percent at factor 2.0.
The overnight share that reproduces the Box 1 order under a standard cross-credit. The number depends on the duplication factor, so the factor is always stated beside it.
The curve is blank below the Line 5c floor, where the order is no longer a cross-credit and cannot be expressed as an implied overnight share.
Source: model/box1_fix.py · model/charts/fig3_credit.py ·
data (CSV) ·
printed run
Below the Worksheet’s income floor, this relationship cannot be expressed at all
At $400 and $250 a week for the other parent (both above the worked example’s $570 but shown here because the floor sits nearby), the printed run marks the implied-overnight-share columns “n/a.” Below $391 a week of the other parent’s available income, Line 5c substitutes a fixed shaded-area amount rather than a percentage of income, so the Box 1 order is no longer a cross-credit and no overnight share can be backed out of it. The chart’s curve is left blank over that range rather than showing a number that would not mean what it appears to mean.
What this does and doesn’t show
Every figure on this page comes from one fact pattern: three children, equal parenting time, no child care claimed, at the incomes stated. The mechanism (Box 1’s credit equalling the payor’s own capped Line 6e) is a property of the form itself and does not depend on the fact pattern; the specific dollar amounts and percentages do. This page says nothing about Box 2, about primary custody, or about any arrangement other than equal time.
Check it yourself
Every number above is printed by a committed script and backed by a CSV of the plotted values.