What the Child Tax Credit is
The Child Tax Credit is a federal credit generally connected to a qualifying child under age 17. It reduces federal income tax after the combined CTC and ODC amount is tested against modified AGI.
A selected row is modeled only when the submitted age, SSN, U.S.-status, dependency, and taxpayer-identification confirmations pass the calculator’s mechanical screening. That screen is not a legal eligibility decision.
What the Credit for Other Dependents is
ODC may apply to a dependent who is not being used for CTC, including when the person does not satisfy the CTC age or identification rules but independently satisfies ODC rules.
ODC is part of the combined nonrefundable dependent-credit calculation. The calculator never automatically moves an excluded CTC child into ODC.
What the Additional Child Tax Credit is
ACTC is the potentially refundable portion associated with qualifying CTC children. It can use credit left after the nonrefundable CTC/ODC portion, subject to earned-income and per-child limits.
Potentially refundable does not mean the displayed amount is the final refund. Withholding, payments, other credits, and the complete return determine an actual refund or balance due.
The 2026 $2,200 Child Tax Credit amount
For this 2026 planning model, each screened-in CTC child creates $2,200 of potential CTC before the combined MAGI phaseout and tax-liability limit.
The $2,200 amount is not automatically refundable. The refundable ACTC is calculated separately and uses a lower per-child cap.
The 2026 $1,700 refundable limit
Modeled ACTC cannot exceed $1,700 for each eligible CTC child. One child therefore has a $1,700 aggregate cap even if earned income produces a larger 15% amount.
ACTC is also capped by credit unused after the nonrefundable portion, so the $1,700 figure is a ceiling rather than an automatic amount.
The $500 Credit for Other Dependents
Each screened-in ODC dependent creates $500 of potential ODC before the combined MAGI phaseout. ODC uses the same combined phaseout computation as CTC.
ODC is nonrefundable in this model. An ODC-only scenario cannot create ACTC even when earned income is high.
Who may be a qualifying child
A qualifying child analysis can involve relationship, age, residency, support, dependent, joint-return, citizenship or residency, and identification requirements.
The form records confirmations but does not prove those facts, apply every exception, or determine which taxpayer may claim the child.
The under-age-17 rule
The modeled CTC category requires the child to be age 16 or younger at the end of 2026. A child who turns 17 during 2026 is not under age 17 at year end.
ODC may be worth reviewing when a dependent is too old for CTC, but the calculator does not automatically reclassify the row.
Relationship, residency and support tests
Relationship, residency, and support rules depend on complete facts and can include exceptions. A checked box means only that the user submitted a confirmation.
Use return records and current instructions to evaluate temporary absences, special placements, support, and joint-return exceptions.
Why claiming someone as a dependent matters
The model requires a selected person to be submitted as claimed as a dependent. Merely supporting a person or living with a child does not by itself establish credit eligibility.
Dependency rules can differ from household expectations, so unresolved facts should be reviewed before relying on an estimate.
Social Security number requirements for CTC and ACTC
A modeled CTC child must have a work-eligible SSN issued by the applicable return due date. Selecting an ITIN or ATIN option does not satisfy the modeled CTC identification requirement.
The form asks only for an identification category. It never requests or validates an actual Social Security number.
TIN requirements for ODC
The ODC screen accepts a timely SSN, ITIN, or ATIN category, subject to the other submitted dependency and U.S.-status confirmations.
TaxArith does not inspect a document, verify when it was issued, or determine whether an identifier is valid for the actual return.
Taxpayer identification requirements
CTC and ACTC require the taxpayer, or at least one spouse on a joint return, to satisfy the submitted work-eligible SSN confirmation. Missing confirmation removes selected CTC children without converting them to ODC.
ODC uses a separate taxpayer-and-spouse identification confirmation. Missing it removes modeled ODC but does not change a row’s chosen category.
How modified adjusted gross income affects the credit
The calculator treats entered modified AGI as a separate phaseout input. It does not infer MAGI from taxable ordinary income, dividends, or capital gain.
Potential CTC and ODC are combined first, and one phaseout reduction is applied to that combined amount.
The $400,000 MFJ phaseout threshold
Married Filing Jointly uses a $400,000 modified-AGI threshold. MAGI exactly at the threshold creates no phaseout reduction.
This credit threshold is separate from federal income-tax brackets and preferential capital-gain thresholds.
The $200,000 threshold for other filing statuses
Single, Married Filing Separately, Head of Household, and Qualifying Surviving Spouse all use a $200,000 phaseout threshold in this calculator.
Qualifying Surviving Spouse can share some joint-return tax parameters, but it does not receive the $400,000 CTC phaseout threshold here.
Why phaseout rounds excess MAGI up to $1,000
The phaseout reduces credit by $50 for each $1,000, or fraction of $1,000, above the threshold. Even $0.01 of excess creates one $50 unit.
TaxArith uses Math.ceil on excess MAGI divided by $1,000. It does not use ordinary rounding or a continuous 5% calculation.
How the nonrefundable credit is limited by tax liability
Other nonrefundable credits first reduce federal tax to nonnegative available tax liability. Combined CTC/ODC used is the smaller of that liability and credit after phaseout.
The nonrefundable portion cannot make displayed federal income tax negative, and the model does not invent an allocation between CTC and ODC when liability is limited.
How refundable ACTC is calculated
Standard ACTC is the smallest of unused credit, the $1,700-per-child aggregate cap, and 15% of earned income above $2,500.
ACTC is zero without an eligible CTC child, when no credit is unused, when the taxpayer SSN requirement is missing, or when Form 2555 is selected.
The $2,500 earned-income threshold
Only earned income above $2,500 enters the standard ACTC percentage. Earned income at or below that threshold produces a zero earned-income ACTC amount.
Nontaxable combat pay is shown separately and is not added automatically; enter earned income after applying any relevant election under official instructions.
The 15% earned-income calculation
After subtracting the $2,500 threshold and flooring the result at zero, the calculator multiplies the remaining earned income by 15% without intermediate cent rounding.
The resulting amount remains subject to unused-credit and per-child refundable caps.
The alternative method for three or more qualifying children
With at least three screened-in CTC children and an explicit election, the model subtracts submitted EITC and other offsets from eligible payroll and related taxes, never below zero.
It compares that alternative base with the earned-income amount, then applies unused-credit and $1,700-per-child caps. Actual Schedule 8812 and worksheet lines still require verification.
Why ODC is not refundable
ODC can reduce available federal income-tax liability but does not independently create ACTC. A return with only ODC dependents has zero modeled refundable dependent credit.
Any ODC left because liability is insufficient is shown as unavailable, not as a refund or carryforward.
How Form 2555 affects ACTC
When the submitted answer says Form 2555 was or will be filed, modeled ACTC is zero. The calculator still computes potential and nonrefundable CTC/ODC.
The warning appears in the submitted result so the effect remains stable until another valid calculation is requested.
Why a tax credit is different from a deduction
A deduction generally reduces income subject to tax. A credit instead reduces calculated tax, subject here to phaseout, tax-liability, and refundability rules.
The potential $2,200 CTC is therefore not equivalent to a $2,200 deduction and should not be multiplied by a marginal rate.
Why ACTC is not the same as the final refund
ACTC is one potentially refundable credit component. A final refund or amount due also reflects withholding, estimated payments, other taxes, credits, and return adjustments.
TaxArith displays ACTC separately and never labels it as a guaranteed refund.
Custody and divorced-parent considerations
Custody, release-of-claim rules, residency, and divorced- or separated-parent provisions can change who may claim a dependent or credit.
A review checkbox flags these facts but does not resolve them. Consult current instructions and professional advice for competing claims.
Why the same dependent cannot be used twice
Each submitted row has one category: CTC, ODC, or not evaluated. The calculator never counts one row as both a CTC child and an ODC dependent.
Duplicate labels are allowed because they are local descriptions, but users should not create duplicate rows for the same person.
Records commonly used for Schedule 8812
Common records may include the prior return, dependent and residency records, identification-document issuance information, earned-income records, payroll-tax records, and custody documents where applicable.
This calculator does not upload or inspect records, populate Form 1040, prepare Schedule 8812, or execute an official Credit Limit Worksheet.
Official data and update status
The 2026 amounts, phaseout structure, earned-income formula, identification requirements, and Schedule 8812 structure were reviewed on August 11, 2026 using IRS Revenue Procedure 2025-32 and current IRS materials.
The available 2026 Schedule 8812 was still marked draft when reviewed. TaxArith is a planning model, not an official IRS calculator or form-preparation tool.