Methodology
How CliffEdge calculates your headroom.
Every formula, every data source, and every engineering decision that shapes what you see in the calculator. If you want to verify our math, this is where to start.
Two MAGI definitions. Used separately.
ACA MAGI and IRMAA MAGI are not the same number. They start from the same AGI but apply different add-backs. Using the wrong definition produces the wrong cliff threshold. CliffEdge computes both independently and never conflates them.
Used for
ACA Subsidy Cliff
Compared against 400% FPL threshold
Start with AGI (Line 11 of Form 1040)
Add back any student loan interest deduction
Add back any IRA deduction
Add back any excluded foreign income
Do NOT add back traditional IRA contributions if taken above the line
Social Security income is included at the gross (not taxable) amount
Result = ACA MAGI — compared against 400% FPL threshold
Used for
IRMAA Medicare Surcharges
Uses income from 2 years prior (lookback)
Start with AGI (Line 11 of Form 1040)
Add back any tax-exempt interest income (municipal bond income)
Add back any excluded foreign income
Do NOT add back IRA deductions
Social Security income is included at the gross amount
Result = IRMAA MAGI — compared against IRMAA tier thresholds
Note: CMS uses your MAGI from two years prior (the "lookback")
Data sources.
Tax brackets, standard deductions, Social Security taxation thresholds, NIIT, LTCG rates, OBBBA deduction phase-out
View Source ↗IRMAA surcharge tiers and thresholds for Medicare Part B and Part D
View Source ↗Federal Poverty Level guidelines for ACA subsidy cliff calculations
View Source ↗Tax table currency.
Every threshold is stored in a versioned data file with a source URL and a last-verified date. This table reflects the current state of each data file — not a hardcoded snapshot.
Income Tax Brackets & Standard Deductions
Tax Torpedo / LTCG Stacking →Agency
IRS
Verified
2026-06-08
Source
View →OBBBA Senior Deduction Phase-Out
OBBBA Senior Deduction →Agency
IRS / Congress
Verified
2026-06-05
Source
View →IRMAA brackets are confirmed each November by CMS. FPL guidelines are published each January by HHS. IRS brackets are published in the annual Revenue Procedure (typically November). OBBBA thresholds are currently not inflation-adjusted.
Engineering principles.
Never hardcode a threshold
All thresholds come from versioned JSON files in the codebase (data/2026/). Each file includes the source URL and the date it was last verified. When IRS or CMS publishes updated figures, the JSON table is updated and the version is incremented. No threshold is embedded in application logic.
Always show the steps
Every function in CliffEdge's calculation engine returns a steps[] array alongside the numeric result. This array contains ordered plain-English sentences explaining exactly how the result was derived. The UI renders these steps as the Show Your Work output. A function that returns only a number is considered incomplete.
No recommendations
CliffEdge computes headroom — the distance between your current MAGI and each cliff threshold. It does not compute an optimal Roth conversion amount, suggest asset allocation, or recommend any action. Optimization requires knowing your goals, time horizon, and estate plans. Showing the boundary is honest. Crossing it for you is not.
Local-first calculation
The calculation engine runs entirely in your browser. No income data, MAGI figure, or cliff result is transmitted to our servers, including data encoded in a Shared Link, which browsers never send over the network. This is an architectural constraint enforced at the code level: engine modules cannot import from network-capable modules, and the engine has no HTTP client.
Limitations & disclaimer.
CliffEdge models federal tax rules only. State income taxes, estate taxes, Medicaid rules, and other jurisdiction-specific costs are not included. Every result is an approximation based on the inputs you provide — actual tax liability depends on your complete tax return, including deductions, credits, and carryforwards.
Tax law changes frequently. Although we update threshold tables annually, CliffEdge cannot guarantee that every figure is current. Always verify critical numbers against primary IRS, CMS, and HHS sources before making a decision.
CliffEdge is not a financial advisor, tax advisor, or registered investment advisor, and is not registered as a broker-dealer. It does not hold itself out as any of these. Nothing on this site constitutes financial, tax, legal, or investment advice. Consult a qualified professional before acting on any information presented here.