Calculation Methodology | Texas Child Support Calculator

1. Filing Assumptions

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The calculator assumes the following baseline filing status for the obligor (person paying support):

Assumption	Value	Source
Tax Year	2026	IRS Rev. Proc. 2025-32
Filing Status	Single Filer	TFC §154.062
Standard Deduction	$16,100	IRS 2026 / OBBBA
State Income Tax	$0 (Texas has no state income tax)	TX Const. Art. VIII, §24-a

Why Single Filer? Texas Family Code §154.062(b) requires the court to calculate net resources based on the obligor's individual income. The standard deduction for a single filer ($16,100 for 2026) is used as the default. This matches the TX Attorney General’s Revised 2025 Tax Charts (effective Sept 1, 2025), which use 2026 federal parameters because the charts are designed for use from Sept 2025 through Aug 2026. The OBBBA adjustment is reflected in the 2026 standard deduction.

No itemized deductions are applied. The calculator uses the standard deduction to keep calculations reproducible and aligned with the AG’s approach of using the simplest reasonable tax burden.

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2. Federal Income Tax Brackets

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Federal income tax is computed using the 2026 marginal tax brackets for a single filer. These rates match the TX Attorney General’s Revised 2025 Tax Charts (effective Sept 1, 2025), which use 2026 federal parameters. Rates are applied to taxable income, derived from annual gross income after deductions.

// Step 1: Determine taxable income
Taxable Income = Annual Gross − Half SE Tax − $16,100 (standard deduction)

// Step 2: Apply marginal brackets (see table below)
// Step 3: Sum tax from each applicable bracket

Rate	Taxable Income Range	Tax on Lower Brackets	Marginal Computation
10%	$0 – $12,400	$0.00	taxable × 0.10
12%	$12,400 – $50,400	$1,240.00	$1,240.00 + (taxable − $12,400) × 0.12
22%	$50,400 – $105,700	$5,800.00	$5,800.00 + (taxable − $50,400) × 0.22
24%	$105,700 – $201,775	$17,966.00	$17,966.00 + (taxable − $105,700) × 0.24
32%	$201,775 – $256,225	$41,024.00	$41,024.00 + (taxable − $201,775) × 0.32
35%	$256,225 – $640,600	$58,448.00	$58,448.00 + (taxable − $256,225) × 0.35
37%	Over $640,600	$192,979.25	$192,979.25 + (taxable − $640,600) × 0.37

// Example: Annual Gross = $60,000, no SE income
Taxable = $60,000 − $0 − $16,100 = $43,900

Tax = $1,240.00 + ($43,900 − $12,400) × 0.12
Tax = $1,240.00 + $31,500 × 0.12
Tax = $1,240.00 + $3,780.00 = $5,020.00/year
Monthly = $5,020.00 ÷ 12 = $418/month

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3. Employee FICA (Social Security & Medicare)

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For W-2 employees, the employer withholds the employee’s share of FICA. The calculator computes this as follows:

Component	Rate	Base / Cap	Source
Social Security (OASDI)	6.2%	First $184,500 of wages	SSA 2026
Medicare (HI)	1.45%	All wages (no cap)	IRS Topic 751
Additional Medicare Tax	0.9%	Wages over $200,000 (single) — not applied by TX AG	IRS Add. Medicare

// Employee FICA computation (matches TX AG methodology)
SS = min(Annual Wages, $184,500) × 0.062
Medicare = Annual Wages × 0.0145

Monthly FICA = (SS + Medicare) ÷ 12

SS Wage Base Cap: Social Security tax only applies to the first $184,500 of wages (2026). Income above this threshold is not subject to the 6.2% SS tax. Medicare has no cap — all wages are subject to 1.45%.

Additional Medicare Tax (0.9%): The IRS imposes a 0.9% Additional Medicare Tax on wages above $200,000 (single filer). However, the TX Attorney General’s calculator does not apply this tax. To match the AG’s methodology and ensure our numbers align with what courts see, this calculator also omits the Additional Medicare Tax from its auto-calculation. Users can manually increase the FICA slider to include it if desired.

// Example: Annual Wages = $84,000
SS = $84,000 × 0.062 = $5,208.00
Medicare = $84,000 × 0.0145 = $1,218.00
Add. Medicare = $0 (below $200K threshold)

Total FICA = $5,208 + $1,218 = $6,426.00/year
Monthly = $6,426.00 ÷ 12 = $536/month

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4. Self-Employment Tax

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Self-employed individuals pay both the employer and employee portions of Social Security and Medicare (commonly called “SECA”). The IRS allows a deduction for the “employer half” of SE tax when computing adjusted gross income.

Component	Rate	Applied To
SE Tax Base	92.35%	Net SE income (simulates employer-half deduction)
SS (employer + employee)	12.4%	SE Tax Base, capped at $184,500
Medicare (employer + employee)	2.9%	SE Tax Base (no cap)
Additional Medicare	0.9%	SE Tax Base over $200,000 — not applied by TX AG

// Self-Employment Tax computation (matches TX AG methodology)
SE Tax Base = Annual SE Income × 0.9235

SS = min(SE Tax Base, $184,500) × 0.124
Medicare = SE Tax Base × 0.029

Total SE Tax = SS + Medicare

// Half-SE-Tax deduction (reduces taxable income for federal tax)
Half SE Tax = Total SE Tax ÷ 2
Taxable Income = Gross − Half SE Tax − $16,100 (standard deduction)

Important: The half-SE-tax deduction reduces taxable income for federal income tax computation (Section 2 above), but does not reduce gross income for child support purposes. The full SE tax amount is treated as an allowable deduction from gross resources per TFC §154.062(d).

// Example: Monthly SE income = $7,000 ($84,000/year)
SE Tax Base = $84,000 × 0.9235 = $77,574.00

SS = $77,574 × 0.124 = $9,619.18
Medicare = $77,574 × 0.029 = $2,249.65
Add. Medicare = $0 (below $200K)

Total SE Tax = $9,619.18 + $2,249.65 = $11,868.83/year
Monthly = $989/month

// For federal income tax computation:
Half SE Tax = $11,868.83 ÷ 2 = $5,934.42
Taxable = $84,000 − $5,934.42 − $16,100 = $61,965.58

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5. Allowable Deductions from Gross Resources

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Texas Family Code §154.062(d) specifies which deductions are permitted when computing net resources from gross resources. Only these specific items may be deducted:

Deduction	Allowed?	Source
Federal Income Tax (single, $16,100 std deduction)	✓ Yes	§154.062(d)(1)
Social Security (FICA / SECA)	✓ Yes	§154.062(d)(2)
Union Dues	✓ Yes	§154.062(d)(5)
Health / Dental Insurance — Child(ren)'s Portion	✓ Yes	§154.062(d)(5)
Vision Insurance — Child(ren)'s Portion	* By agreement/order	See §9 below
State Income Tax	N/A — Texas has no state income tax	—

// Net Resources computation — TFC §154.062(d)
Net Resources = Gross Income − Federal Tax − FICA/SE Tax − Union Dues − Insurance for Child(ren)

// Health and dental insurance for the child(ren) is an allowable
// deduction under §154.062(d)(5), same as taxes and FICA.
// See Section 9 for vision insurance treatment.

Insurance as Deduction: Per TFC §154.062(d)(5), the cost of health insurance and dental insurance for the obligor’s child is an allowable deduction from gross resources — it reduces net resources before the guideline percentage is applied. This is the same treatment as federal income tax and FICA. See Section 9 for details.

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6. Net Resources Cap

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Texas law caps the amount of net resources to which the guideline percentage is applied. Above this cap, support is at the court’s discretion.

Parameter	Value	Source
Net Resources Cap	$11,700/month	TFC §154.125(a)-(a-1)
Effective Date	September 1, 2025	TFC §154.125
Above-Cap Treatment	Discretionary — court may order additional support	TFC §154.126

// Net Resources capping
if (Net Resources > $11,700) {
Net Resources = $11,700 // guideline cap applied
// Court may order above-guideline support per §154.126
}

Above-Cap Income: When an obligor’s net resources exceed $11,700/month, the court applies the guideline percentage only to the first $11,700. The court may order additional support above the guidelines, considering the proven needs of the child, per TFC §154.126. This calculator applies the statutory cap and does not estimate above-cap discretionary amounts.

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7. Guideline Percentages

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When the obligor has children only with the custodial parent (no other children to support), the base guideline percentages apply:

Children Before the Court	Percentage of Net Resources	Source
1 child	20%	TFC §154.125(b)
2 children	25%	TFC §154.125(b)
3 children	30%	TFC §154.125(b)
4 children	35%	TFC §154.125(b)
5+ children	40%	TFC §154.125(b)

// Base support computation
Base Support = Net Resources (capped) × Guideline Percentage

// Example: 2 children, Net = $5,000/month
Base Support = $5,000 × 0.25 = $1,250/month

When the obligor has children with other partners in addition to the children before the court, a multi-family adjustment applies. See Section 8.

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8. Multi-Family Adjustment Table

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When the obligor has a duty to support children from multiple relationships, the guideline percentage is reduced per the table below. This ensures the obligor’s total support obligations across all families remain reasonable.

Full Multi-Family Percentage Matrix (TFC §§154.128–129)

Children Before Court	0 Other	1 Other	2 Other	3 Other	4 Other	5 Other	6 Other	7 Other
1 child	20.00%	17.50%	16.00%	14.75%	13.60%	13.33%	13.14%	13.00%
2 children	25.00%	22.50%	20.63%	19.00%	18.33%	17.86%	17.50%	17.22%
3 children	30.00%	27.38%	25.20%	24.00%	23.14%	22.50%	22.00%	21.60%
4 children	35.00%	32.20%	30.33%	29.00%	28.00%	27.22%	26.60%	26.09%
5 children	40.00%	37.33%	35.43%	34.00%	32.89%	32.00%	31.27%	30.67%
6 children	40.00%	37.71%	36.00%	34.67%	33.60%	32.73%	32.00%	31.38%
7 children	40.00%	38.00%	36.44%	35.20%	34.18%	33.33%	32.62%	32.00%

// Multi-family lookup
Adjusted % = MULTI_PCT[childrenBeforeCourt][otherChildren]

// Example: 2 children before court, 1 other child
Adjusted % = MULTI_PCT[2][1] = 22.50%
Base Support = $5,000 × 0.225 = $1,125/month
// vs. $1,250 with no other children (25%)

How “Other Children” Works: “Other children” means children the obligor has a legal duty to support who are not before the court in this case. This includes biological children, adopted children, and children for whom the obligor has been ordered to pay support in another proceeding.

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9. Insurance Treatment

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Health and dental insurance premiums for the child are expressly listed as allowable deductions under TFC §154.062(d)(5). They are deducted from gross resources — the same treatment as federal income tax, FICA, and union dues — reducing net resources before the guideline percentage is applied.

// Insurance for the child is DEDUCTED from gross resources — TFC §154.062(d)(5)

Total Deductions = Fed Tax + FICA/SE + Union Dues + Health Ins + Dental Ins
Net Resources = Gross Income − Total Deductions
Guideline Support = Capped Net Resources × Guideline %

// Example: Gross = $8,000/mo, $300 health ins, 1 child (20%)
Fed Tax = $1,024.17 FICA = $612.00 Health Ins = $300
Net = $8,000 − $1,024.17 − $612.00 − $300.00 = $6,063.83
Support = $6,063.83 × 20% = $1,212.77/month

Statutory Basis: TFC §154.062(d) enumerates the allowable deductions from gross income. Subsection (d)(5) specifically includes “expenses for the cost of health insurance, dental insurance, or cash medical support for the obligor’s child ordered under Section 154.182 or 154.1825.” This calculator assumes the obligor provides the insurance.

Vision Insurance: TFC §154.062(d)(5) expressly references health insurance and dental insurance but does not specifically enumerate vision insurance. Vision coverage may be included by agreement of the parties or by separate provision in the court’s order. When vision insurance is entered in the calculator, it is treated as an additional allowable deduction for calculation purposes. Any decree or order should address vision coverage as a separate line item.

When the Custodial Parent Carries Insurance: If the obligee (custodial parent) provides the insurance rather than the obligor, TFC §154.182(b-1) and §154.183 direct the court to order the obligor to pay the actual cost of coverage as “additional child support.” In that scenario, the insurance cost would be added to the base obligation rather than deducted. This calculator assumes the more common arrangement where the obligor provides the coverage.

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10. Reverse Mode (Support → Income)

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Reverse mode works backward: given a desired child support amount, it estimates the gross income required to produce that obligation. This is inherently an approximation because income tax and FICA are progressive (the deduction rate depends on the income level being solved for).

// Reverse mode approximation
// Assumes ~20% effective deduction rate for tax + FICA

Target Support = User Input

Approximate Net = Target Support ÷ Guideline %
Approximate Gross = Net ÷ (1 − 0.20)

// The 20% approximation is a reasonable median for most income ranges
// Actual effective rate varies by income level

Estimation Only: Reverse mode results are approximate. The 20% effective deduction rate assumption works well for moderate incomes ($40K–$120K/year) but may over- or under-estimate at extreme income levels. Use forward mode for precise calculations, or consult a family law attorney for above-guideline scenarios.

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11. Statutory References

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All calculations in this tool are derived from the following Texas Family Code provisions and IRS publications:

Reference	Subject	Link
TFC §154.062	Net resources; allowable deductions	View Statute ↗
TFC §154.125	Guideline percentages; net resources cap ($11,700)	View Statute ↗
TFC §154.126	Above-guidelines support; proven needs of child	View Statute ↗
TFC §§154.128–129	Multiple families; adjusted percentages	View Statute ↗
IRS Rev. Proc. 2025-32	2026 tax brackets; standard deduction ($16,100)	View IRS ↗
SSA Contribution Base	2026 Social Security wage base ($184,500)	View SSA ↗
IRS Topic 751	FICA / Social Security & Medicare taxes	View IRS ↗
IRS SE Tax	Self-employment tax (Schedule SE)	View IRS ↗
IRS Add. Medicare	Additional Medicare Tax (0.9% over $200K) — exists in IRS code but not applied by TX AG	View IRS ↗
OBBBA (2025)	One Big Beautiful Bill Act — increased standard deduction (reflected in 2026 rate of $16,100)	View Bill ↗
TX AG Tax Charts	Revised 2025 Tax Charts (eff. Sept 1, 2025) — uses 2026 federal parameters	View PDF ↗

Transparency Commitment: Every formula, rate, cap, and percentage in this calculator is sourced from publicly available statutes and IRS publications. If any rate changes due to legislative action or annual inflation adjustments, this methodology page will be updated to reflect the current values.

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