How to Split Nanny Share Costs Between Two Families

A nanny share is the best-value in-home childcare most families can get, and the fastest way to lose a friendship. Both outcomes come from the same source: the money is more complicated than “we’ll split it.”

Split 50/50 and it works until the week one family goes on holiday, or one child starts preschool three mornings, or one family needs an extra hour on Thursdays. Then someone is quietly paying for care they aren’t using, nobody wants to be the one to raise it, and it festers.

This is the method that doesn’t do that. It’s an offshoot of tracking childcare costs properly — same principle, applied to two households.

Step 1: Total the real employer cost, not the hourly rate

The hourly rate is what your nanny earns. It is not what the arrangement costs. A household employer also owes payroll taxes and, in most states, carries workers’ compensation insurance.

Say the share agrees on $25/hour gross, 40 hours a week, 50 weeks a year (two weeks unpaid or covered by the nanny’s paid leave — agree which).

That’s $54,925, not $50,000 — about 10% on top. Workers’ comp premiums and payroll service fees vary; state unemployment insurance may add more depending on where you are. Use your own quotes, but never budget off gross wages alone.

Two notes before you go further:

• Overtime. Nannies are non-exempt under federal law, and a live-out nanny is owed 1.5× for hours over 40 in a week. In a share there’s one worker, so both families’ hours count toward the same 40. Build the schedule under 40 or budget for overtime explicitly.
• The household-employer threshold. Once cash wages to a household employee pass the IRS’s annual threshold, withholding and filing obligations kick in. The current figure is in Publication 926 — check it for the year in question rather than relying on a number you half-remember.

Step 2: Convert to a true cost per hour

Total all-in cost ÷ total scheduled hours.

$54,925 ÷ (40 × 50) = $54,925 ÷ 2,000 = $27.46 per hour

That $27.46 — not $25 — is the number every split should be built on. Using $25 leaves nearly $5,000 a year unallocated, and it always ends up landing on whichever family is doing the payroll.

Step 3: Separate shared hours from solo hours

Here’s where the 50/50 split breaks and this method doesn’t.

Assume:

• 25 hours a week both children are present — shared hours
• 15 hours a week only Family A’s child is present (Family B’s child is at preschool those mornings) — solo hours, Family A

Over 50 weeks: 1,250 shared hours and 750 solo hours for Family A.

The rule: shared hours split evenly; solo hours are billed entirely to the family using them.

It reconciles exactly — the two shares add to the full employer cost, with nothing unallocated.

Monthly, that’s about $3,147 for Family A and $1,430 for Family B. Very different numbers, both defensible, and neither requires anyone to have an awkward conversation — the schedule produced them.

Why this method holds up

It survives schedule changes. Family B’s child drops a preschool morning and joins the share? Move 3 hours from solo to shared. Recalculate. Done — no renegotiation.

It handles holidays honestly. If your agreement pays the nanny when a family is away (it should — she’s not available for other work), those hours stay in the paying family’s column. That’s the point: you’re paying for a reserved schedule, not for attendance.

It scales to a 60/40 starting point. Some shares agree from the outset that the family hosting the share pays less, or that the family with the toddler pays more than the family with the infant. Fine — apply the weighting to the shared-hour split (say 60/40 instead of 50/50) and leave the rest of the method intact.

Step 4: Decide who is the employer — before the first pay run

This is the part families skip and later regret. Two structures:

Both families are employers. Each registers as a household employer, each has its own EIN, each pays its own share of wages directly and files its own returns. More admin, but each family is straightforwardly paying for its own childcare — which matters because you can only count expenses you actually paid as your qualified childcare expenses for a Dependent Care FSA or the child and dependent care credit.

One family is the sole employer, the other reimburses. Simpler payroll. But the reimbursing family isn’t paying wages to a care provider — it’s reimbursing another family — which can complicate its own tax position, and it puts all the legal employer obligations on one household.

Most payroll services that handle nanny shares support the two-employer structure specifically because of the tax treatment. Get advice on which structure fits before you start, not in February.

The written agreement — a copy-ready checklist

Every share should have one. Ten lines, agreed before day one:

1. Hourly rate and how and when it will be reviewed.
2. The schedule — shared hours and solo hours, per family, per week.
3. The cost-per-hour calculation, including which employer costs are in it.
4. Overtime — how it’s triggered and which family bears it.
5. Holiday and sick pay — how many paid days, and who pays when only one family is away.
6. What happens if one family goes away for a week — do they still pay their share?
7. Notice period if a family leaves the share, and what the remaining family owes meanwhile.
8. Whose home, and any compensation for hosting (utilities, wear, supplies).
9. Who is the employer and who runs payroll.
10. Expenses — food, outings, mileage if the nanny drives, and how they’re split.

Number 7 is the one that causes the most damage when it’s missing. If Family B moves away, Family A is suddenly liable for a full-time nanny at $54,925 a year with no notice. A 60-day notice clause is worth more than any of the others.

Is it actually cheaper than a centre?

Run the numbers side by side rather than assuming. Family B above pays about $17,164 a year for 25 hours a week of in-home care with no closure days and no late-pickup fees. Family A pays $37,761 for 40 hours. Compare each against a centre’s true year-one cost — not its tuition — using the method in how to compare daycare costs between two providers. The comparison often surprises people in both directions.