Clear assumptions. Checkable estimates.

How we check our calculations

Different checks provide different kinds of evidence. Together they help us review supported planning scenarios; they do not establish complete tax-return accuracy.

1. Independently derived 2026 reference cases. Expected planning results are derived separately from the application’s calculation code, then compared with its outputs.
2. Automated regression tests. Tests check defined behaviors and safeguards so changes are less likely to alter previously checked results unexpectedly.
3. External federal tax comparisons. The financial validation report records 59 regular federal income tax comparisons matching Tax-Calculator 6.8.5 for supported scenarios. That comparison does not validate ACA eligibility or a complete tax return.
4. Manual checks through the deployed app. The merged November 5, 2026 report records a human tester’s verification of eight financial scenario groups, with all eight reported as matching expected reference results. The report preserves that tester attribution; it is not an independently reproduced, field-by-field audit.
5. Documented limits. The application documents unsupported financial situations, assumptions that require review, and known differences between planning estimates and filing methods.

The validated capital gains ACA threshold example

The homepage transcribes the independently derived 2026 capital gains example, not a fabricated application screenshot. Married filing jointly, an ACA household of four in the contiguous United States/DC, and full-year eligible Marketplace coverage are held constant.

Both scenarios include $27,000.00 in nonqualified dividends and $13,000.00 in qualified dividends. Realized long-term capital gains rise from $88,600.00 to $88,600.01, making ACA MAGI $128,600.00 and $128,600.01. There are no wages, retirement withdrawals, Roth conversions, other income adjustments, losses, or carryforwards. The base standard deduction is $32,200.

Hypothetical selected-plan and benchmark Silver premiums are $2,500 and $3,000 per month for January–December, not real quotes. Required eligibility conditions are assumed satisfied and advance credits are explicitly $0 for all months.

At the modeled 400% threshold ($128,600.00, using the four-person $32,150 poverty guideline for 2025), final estimated annual premium tax credit is $23,191.44. One cent above it, the modeled credit is $0.00. Federal regular income tax is $0.00 in both cases. Net annual insurance cost and combined modeled federal tax plus insurance cost each rise from $6,808.56 to $30,000.00: a $23,191.44 increase.

Qualified dividends and eligible long-term gains receive preferential federal treatment but still count toward ACA MAGI. This does not mean realizing gains is inherently a poor choice or that every additional dollar causes a cliff. Actual credits depend on household eligibility, location, age, premiums, and other circumstances.

How this example was checked

The merged application report documents separate high-precision reference calculations with no production-engine imports, automated regression assertions against the stored expectations, and desktop/mobile browser tests entering the scenario through the application. It records 564 unit/integration tests and four browser tests passing, along with TypeScript and production build checks. No financial calculation defect was identified in that validation.

Those are reported application-validation results, not financial suites rerun by this website update. The browser tests used a local production preview; they are not a human audit of the deployed application. The private repository’s capital-gains scenario report is summarized here rather than linked behind an access restriction.

The one-cent boundary is a continuous-model illustration, not a promise of the same change on a filed return. Whole-dollar reporting, final-year instructions, actual eligibility, and Form 1095-A records can affect results. Net insurance cost means selected-plan premiums less final credit, not out-of-pocket medical spending or cash premiums paid during the year.

What the validation does not establish

The application uses regular pre-credit federal income tax estimates and conditional ACA assumptions. Federal estimates use marginal rate schedules rather than final IRS Tax Table bands. ACA estimates use continuous poverty-guideline ratios and contribution calculations; final-year filing instructions, rounding, eligibility, and Form 1095-A records can produce different results.

Planning estimates may differ from actual federal tax returns and Marketplace determinations. These checks are not independent certification, IRS approval, professional tax approval, or comprehensive financial validation.

Current scope and important exclusions

The Income Planner supports annual income modeling, estimated federal income taxes, ACA premium tax credits, Roth conversion exploration, standard investment gains and losses, and scenario comparisons for 2026.

It does not provide state or local income tax calculations, payroll or self-employment tax calculations, complete tax-return preparation, or full health insurance eligibility determinations. Other exclusions include AMT, NIIT, other federal credits, and certain special investment and deduction treatments.

It does not provide comprehensive multi-year retirement projections, portfolio longevity calculations, or Social Security optimization. Unsupported cases and independently supplied eligibility assumptions need review before relying on estimates.

About the supporting documentation

The summaries above reflect the application’s financial validation report, limitations document, illustrative example specification, frozen 2026 reference fixtures, and merged manual production validation report. The application repository is private, so this page provides accessible summaries instead of links that visitors cannot open.

The application’s separate illustrative Example Plan and the earlier retirement-withdrawal threshold cases use different income or premium assumptions. Neither is substituted for the capital gains example shown here.