Shared parenting
More states price joint custody with the cross-credit than with any other formula, and Massachusetts does not use it
While 18 states and the District of Columbia price joint custody with the cross-credit formula, which credits each parent for the time they house the children, Massachusetts has no parenting-time term at all. For the same family that formula orders $701 a week at equal time, and Massachusetts orders $1,013.
A week under the cross-credit formula at equal time
A week under the Massachusetts Worksheet for the same family
One family, equal parenting time, no child care
I pay child support in Massachusetts myself, so I have a stake in the outcome. Every figure on this page is for the worked example used across this site: two incomes of $201,000 and $29,640 a year, three children, equal parenting time and no child care unless stated.
The formula is computed in model/box1_fix.py (Variant B) and measured against ability to pay in model/ability_to_pay.py, checked by model/test_ability_to_pay.py.
The cross-credit charges each parent for the time the other has the children
When both parents house the children, each household pays for a bed, a kitchen and the drive to school. The cross-credit starts from that. It raises the basic support amount by half to cover the costs two households both carry, splits the larger amount between the parents by income, charges each parent for the share of time the children spend with the other, and has the parent who owes more pay the difference.
It is the most common shared-parenting formula. A 2020 survey of state guidelines found it in 23 states and found no other method in use in more than two, Oldham and Venohr, 54 Fam. L.Q. 141, 152.
Worked through for one family, the formula is six lines of arithmetic
The worked example earns $201,000 a year against the other parent’s $29,640, has three children, and splits the time equally. Every figure is weekly.
| Step | Amount |
|---|---|
| Basic support for three children, from the Massachusetts schedule | $1,241 |
| Raised by half for the costs two households both carry | $1,861 |
| The higher earner’s share, 87.7% of the income | $1,632 |
| The other parent’s share | $229 |
| Each parent owes half their share, for the other’s half of the time | $816 and $115 |
| The higher earner pays the difference | $701 |
That order is 26.1% of the payor’s ability to pay, meaning take-home pay less any child care he pays himself. Where each parent pays $300 a week of child care, the $600 should be split on what each household has after tax and after the order. The higher earner then carries 62.8% of it, and the order rises to $778 a week, 32.6% of ability to pay. Split the child care the Worksheet’s way instead, charging the higher earner 87.7% of the other parent’s child care and crediting him 12.3% of his own, and the same cross-credit order would be $927.
Massachusetts charges both households the full amount and then shrinks the credit
The Massachusetts Worksheet puts every child in both households at the full schedule amount and subtracts one from the other. At equal time that is the cross-credit with the basic amount doubled, which assumes two households cost twice what one does. A cap on one line of the Worksheet then cuts the higher earner’s credit by about half. For this family Massachusetts orders $1,013 a week at equal time, only 6.9% below the $1,088 it orders when the other parent has the children full time.
Eighteen states and the District of Columbia use the cross-credit today, and four more states use a version of it
Read from each state’s current guideline.
| State | Added for shared costs | Applies from |
|---|---|---|
| Alabama | 50% | About equal time |
| Alaska | 50% | 30% of the year |
| Colorado | 50% until March 2026, then a table | 93 overnights until March 2026, then from one overnight |
| District of Columbia | 50% | 35% of the year |
| Florida | 50% | 73 overnights |
| Idaho | 50% | More than 25% of overnights |
| Illinois | 50% | 146 overnights (110 from January 2027) |
| Maryland | 50% | 92 overnights |
| Montana | No flat amount | 110 days |
| Nebraska | 50% | More than 142 days |
| New Mexico | 50% | 35% of the year |
| North Carolina | 50% | 123 overnights |
| Oklahoma | 100%, 75% or 50%, falling as time rises | 121 overnights |
| South Carolina | 50% | 110 overnights |
| Vermont | 50% | 30% of the year |
| Virginia | 40% | 91 days |
| West Virginia | 60% | 127 days |
| Wisconsin | 50% | 92 overnights |
| Wyoming | 50% | More than 25% of the year |
Georgia, Michigan, Minnesota and Oregon use a curved version of the same formula, with no threshold. Massachusetts is not on either list.
Federal law should cap every joint-custody order at what the cross-credit produces
The federal rule that governs child support guidelines, 45 C.F.R. § 302.56, says nothing about parenting time. So each state decides, and Massachusetts removed its parenting-time adjustment in 2017 and brought it back as a deviation in 2025. The petition to the Department of Health and Human Services asks for three things. No state could order more for joint custody, meaning each parent has the children at least a third of the time, than the cross-credit at the standard 50% produces. A state could keep its own method so long as it stays under that line. Every order would be capped at 40% of ability to pay. While the Department reviews the method, a joint-custody order would be capped at 30%. The comments to the Chief Justice ask Massachusetts to adopt the same formula now.
The petition weights the formula by each parent’s share of the time, as the states that use it do. Crossing a third of the time then moves the order only a little, and no single night is worth litigating over.
One family at one set of incomes, and a count that depends on the definition
Every dollar figure is for one family, the worked example, so the page shows how the formula treats that one family. The count of 19 jurisdictions depends on the definition. Nevada nets each parent's full amount with no charge for time, and so do Arkansas and Mississippi, so none of them is counted here, though the 2020 survey counts Nevada. North Dakota reduces only one parent's amount and is not counted either. Texas lawyers commonly use the formula in practice, but Texas does not write it into its guideline. With $300 a week of child care from each parent, split after the order, the cross-credit still takes 32.6% of this family's ability to pay, above the 30% interim limit and under the 40% ceiling the petition keeps on every order.