Household Finance DemoDMarried filing jointly, one child. Anchored to fictional pay stubs (Daniel through Oct 22, Maya through Oct 22) and synthetic ledger income through Oct 22; recomputed from the demo dataset. This is a projection, not a filing.
| Daniel W-2 wages (Box 1) | $127,279.44 |
| gross $146,400.00 less pre-tax: 401(k) (8%) $11,712.00 · Benefits (pre-tax) $7,408.56 | |
| Maya W-2 wages (Box 1) | $94,860.00 |
| gross $102,000.00 less her 401(k) at 7% ($7,140.00) | |
| Other contract income | $1,874.33 |
| year-to-date $1,405.75 from the synthetic ledger, paced to a full year | |
| Interest, dividends & other | $681.09 |
| Adjusted gross income | $224,694.86 |
| less the $32,200 standard deduction → taxable income $192,494.86 |
| Tax before credits | $31,772.87 |
| Child tax credit | −$2,000.00 |
| Income tax | $29,772.87 |
| Self-employment tax | $247.18 |
| Total federal tax | $30,020.05 |
| Withholding — Daniel | $15,846.48 |
| Withholding — Maya | $7,856.88 |
| Balance | $6,316.69 due |
The demo withholding comparison allocates the fictional tax projection across Daniel and Maya. Maya's income is about 43% of the household total.
Daniel has 5 paychecks left this year after today. Adding extra withholding on his W-4 (Step 4c) of $1,263.34 per check zeroes the projected federal balance; $662.94 per check reaches the 90%-of-tax safe harbor ($27,018.05) and avoids any underpayment penalty — withholding is currently $3,314.69 short of that line.
For 2027, the structural fix is one Step 3 claim in the household, not two: keep the child credit on Daniel's W-4 and remove it from Maya's. Her withholding then runs about $83 per paycheck higher, which tracks her share of the tax as it is earned.
Sensitivity: if Maya's reduced schedule ($1,416/period) persists instead of resuming, the federal balance falls to $4,793.86. Engine check: run against the filed 2025 return (AGI $158,442.19), this engine produces $19,089.31 vs the filed $19,102.44 — a 0.07% difference.
Sources: Synthetic household model