## Tax timeline
The **Tax Planner** (Planning → Tax) projects taxable income, federal brackets, and estimated taxes **by calendar year** through your planning horizon. Year 0 matches the plan schedule start year. AGI components come from detailed income for that calendar year (January 1 ages and month proration)—the same calendar window as Income page **Ref. yr $** and mix charts—plus Roth conversions, withdrawals, and RMDs so you can spot high-tax years before they happen.
## Federal tax brackets in projections
Analyzer uses a **federal bracket catalog** by filing status and year to estimate ordinary income tax in projections. Bracket boundaries drive the Roth **bracket-filling** tools: they show headroom remaining in your current bracket before the next rate applies. State taxes vary and are simplified—treat results as educational estimates.
## What IRMAA is
**IRMAA** (Income-Related Monthly Adjustment Amount) is a surcharge added to Medicare Part B and Part D premiums when your **MAGI** exceeds tier thresholds. IRMAA uses a **two-year lookback**: your premiums at 65 depend on income reported at 63. Crossing a tier boundary by even one dollar triggers the full surcharge for that tier. 2026 individual tiers start at $109,000 MAGI (double for married filing jointly), rising to a top tier at $500,000 (individual) / $750,000 (joint).
## How Analyzer models IRMAA
Analyzer's tax projection applies IRMAA tier tables to your projected MAGI with the two-year lookback, and includes both the Part B and Part D surcharge in detailed Medicare expenses. **IRMAA is assessed per Medicare beneficiary**: a married couple where both spouses are enrolled in Medicare pays the surcharge twice, not once, in years both are covered. Roth conversion tools flag years where a proposed conversion would push MAGI into a higher IRMAA tier.
## Additional Medicare Tax and NIIT
Beyond ordinary brackets, Analyzer's tax projection also models two federal surtaxes for high earners: the **Additional Medicare Tax** (0.9% on wages and self-employment income above $200,000 single / $250,000 married filing jointly) and the **Net Investment Income Tax (NIIT)** (3.8% on investment income above the same thresholds). Both use simplified income proxies rather than the full IRS worksheets, so treat the results as directional estimates.
## Alternative Minimum Tax (AMT)
Analyzer includes a simplified **AMT** calculation: a parallel tax on a broader income base (adding back the standard deduction) at flat 26%/28% rates after an exemption that phases out at high income, compared against your regular tax—you owe the higher of the two. It doesn't capture every AMT preference item (like incentive stock options), so it's a partial picture of AMT exposure, not a full Form 6251 substitute.
## State capital gains treatment
Most states tax long-term capital gains and qualified dividends at the same rate as ordinary income, so Analyzer folds them into the state ordinary tax line (shown as $0 state LTCG). A handful of states give capital gains real preferential treatment and show a nonzero **state LTCG** amount: South Carolina and Wisconsin exclude a percentage of gains, North Dakota and New Mexico apply their own exclusion formulas, Hawaii taxes gains at a flat alternative rate, and Montana uses its own dedicated bracket schedule. Washington's capital-gains excise tax is not modeled.
## Roth conversions, IRMAA, and ACA subsidies
A Roth conversion raises MAGI in the conversion year, which can trigger IRMAA tiers (if you are near Medicare age) or reduce **ACA premium subsidies** (if you buy marketplace health insurance before 65). Analyzer's conversion tools surface these cliffs so you can size conversions below them.
## Education tax credits (AOTC / LLC)
American Opportunity and Lifetime Learning credits use **full-time student** flags and **AOTC years already claimed** on each household member (Settings → Profile), plus **qualified education expense** lines under Planning → Expenses linked to that person—not a flat annual amount on the profile. Tax projections sum those expense lines per plan year. AOTC includes a **40% refundable** portion (up to $1,000), so it can reduce tax below zero even when federal ordinary tax is already $0.
## Child tax credit (nonrefundable)
**Child tax credit (CTC)** in Phase 1 is **nonrefundable**: it only reduces federal ordinary income tax plus LTCG tax. Qualifying children (generally under 17) are counted from household profiles; the potential credit appears before the liability cap. When federal ordinary + LTCG are already $0 after deductions, applied CTC shows **$0**—unused credit does not create a refund. Refundable ACTC is not modeled yet.
Educational content only—not personalized investment, tax, or legal advice.