Complete Technical Manual & Methodology Guide
Master your retirement financial model with the FNC Retirement Engine v4.0. Comprehensive technical guide covering the automated Tax Optimizer, horizon-scanning marginal rate parity, independent spousal age modeling, surviving spouse single-bracket transitions (the "Widow's Penalty"), SECURE 2.0 catch-up tiers, ACA MAGI (IRC §36B), Treasury Reg. §1.408A-6 Roth ordering rules, Medicare IRMAA cliffs, and correlated Monte Carlo simulations.
1. Educational Modeling Only: The FNC Retirement Engine is an independent educational modeling tool built to help users evaluate hypothetical financial strategies. It does not constitute formal financial, investment, legal, or tax advice. Always consult a qualified CPA, Certified Financial Planner (CFP), or tax professional before executing financial moves.
2. Built with Modular Architecture: Engineered using modern ES Modules (Vite, Chart.js 4.x, Tailwind CSS). Report discrepancies or feature requests on YouTube (@FrugalNotCheap) for ongoing updates.
3. Statutory Tax Recency (2026 & SECURE 2.0): Federal income tax brackets, standard deductions, ACA subsidy bands, and contribution limits reflect IRS and statutory procedures for 2026 including SECURE 2.0 super catch-up tiers. Medicare IRMAA tiers reflect CMS 2026 rules. Roth ordering rules reference Treasury Reg. §1.408A-6.
4. Client-Side Processing & Privacy: All calculations execute 100% client-side inside your browser engine. Financial inputs are saved locally in browser storage (localStorage under fnc_planner_state) and are never uploaded to remote servers.
Interface Navigation & Primary Modules
Displays deterministic net worth accumulation and decumulation curves (Taxable, Tax-Deferred, Roth, Cash), annual net cash flows, dynamic Monte Carlo success status card, integrated SWR FI Milestones, and the unified Lifecycle Timeline with anti-overlap 2-tier milestone pins.
Houses custom cash flow life events grouped into Inflows vs. Outflows, 1-click Quick Templates (+Pension, +Inheritance, +College, +Home Sale), Social Security claiming estimator, Roth Conversion Ladder wizard, and IRC §72(t) SEPP schedules.
Automated multi-year tax optimizer that sweeps candidate conversion strategies, calculates After-Tax Estate Wealth passed to heirs, surfaces Adverse Policy Cliff warnings (IRMAA, ACA, 10% penalty), and prevents tax traps with 1-click execution.
Unified decumulation center: select active strategies (Fixed Dollar, Guyton-Klinger, Vanguard Dynamic, VPW, Fixed %, Hebeler), set baseline living budgets, adjust inflation, configure dynamic guardrail floors/ceilings, set tax liquidation sequencing, and view spending trajectory.
Runs 500 to 5,000 correlated randomized trials with independent inflation resets per run. Reports overall success rate, principal preservation rate, 10th percentile bear cases, and peak-to-trough max drawdowns.
Stress-tests your plan starting on Year 1 of retirement against 5 real historical market shock sequences (1929 Great Crash, 1973 Stagflation, 2000 Dot-Com, 2008 GFC, 2022 Rate Shock).
Complete year-by-year financial accounting ledger with calendar year sub-labels Age (YYYY), streamlined Executive View toggle, column collapse toggles, statutory cliff visual highlights, and full CSV spreadsheet export.
fnc_planner_state under SCHEMA_VERSION = 400). Access the 1-Page Retirement Blueprint, export/restore plan states via .JSON, or export audit tables to CSV. Real-time validation warnings highlight input conflicts with 1-click magic auto-fixes.
The Tax Optimizer & Estate Wealth Engine
The v4.0 Tax Optimizer is an automated decision-support engine designed to solve the multi-decade tax arbitrage puzzle. It evaluates whether converting pre-tax dollars to Roth today at known marginal brackets generates higher lifetime spendable income and greater terminal wealth for heirs than leaving assets in Traditional accounts.
Rather than using a static year-by-year heuristic, the optimizer runs a baseline projection to scan your entire horizon. It calculates the Projected Post-RMD Marginal Rate forced on your Traditional accounts at ages 73/75+ and compares it against your Early Retirement Marginal Rate:
• If Future Forced RMD Rate > Current Rate: Substantial tax arbitrage exists. Prepaying taxes at 10% or 12% permanently shields money from future 22%, 24%, or 32% forced brackets.
• If Future Rate ≤ Current Rate: Conversions are deferred to prevent overpaying taxes unnecessarily.
Conventional calculators evaluate only nominal ending net worth. However, $1,000,000 left to heirs has vastly different purchasing power depending on account location:
• Roth IRA: Passes 100% tax-free to heirs; heirs enjoy 10 years of tax-free growth under the SECURE Act ($1.00 on the dollar).
• Taxable Brokerage: Receives a complete step-up in cost basis under IRC §1014; all capital gains are wiped out at death ($1.00 on the dollar).
• Traditional 401(k)/IRA: Fully taxable to non-eligible designated beneficiaries as ordinary income within 10 years, often pushing heirs into 28%+ marginal brackets.
The optimizer ranks strategies by After-Tax Estate Value, accurately capturing this transfer benefit.
Medicare IRMAA Part B & D surcharges are steep cliff thresholds. Going $1 over a threshold incurs $1,150 to $6,940 per person in annual surcharges. The optimizer tests dedicated IRMAA-capped conversion ceilings (e.g. $217,000 for MFJ) that convert maximum pre-tax dollars while maintaining a $1,000 safe buffer below the cliff.
For early retirees drawing health coverage under the ACA before age 65, the optimizer evaluates conversions up to 3.98× FPL, locking in pre-tax distributions without forfeiting premium tax credits or crossing the 400% FPL cliff.
Independent Spousal Setup & The Widow's Penalty
Prior versions assumed both spouses were identical in age. Version 4.0 decouples primary age and spouse age:
• Senior Standard Deduction ($1,650/spouse): Evaluated individually. If one spouse is 66 and the other is 62, only one $1,650 addition applies.
• OBBBA Senior Bonus ($6,000/spouse): Awards $6,000 per spouse who has reached age 65 during calendar years 2025–2028.
• Medicare IRMAA: Only charges Medicare surcharges for the spouse who has attained age 65.
When married retirees lose a spouse, the survivor's tax bracket thresholds and standard deductions are cut in half (transitioning from MFJ to Single), but required minimum distributions (RMDs) from accumulated Traditional accounts remain unchanged.
• Version 4.0 models this automatically: when simulated age exceeds Spouse End Age, the engine switches active filing status to Single.
• This exposes the true tax risk of deferring conversions, highlighting the advantage of aggressive pre-tax liquidation while both spouses are alive.
Federal Brackets, Roth Accounting & IRMAA
1. Statutory 2026 Federal Income Tax Brackets (Taxable Income)
| Rate | Married Filing Jointly (MFJ) | Single | Head of Household (HoH) | Married Filing Separately (MFS) |
|---|---|---|---|---|
| 10% | $0 – $24,800 | $0 – $12,400 | $0 – $17,700 | $0 – $12,400 |
| 12% | $24,801 – $100,800 | $12,401 – $50,400 | $17,701 – $67,450 | $12,401 – $50,400 |
| 22% | $100,801 – $211,400 | $50,401 – $105,700 | $67,451 – $105,700 | $50,401 – $105,700 |
| 24% | $211,401 – $403,550 | $105,701 – $201,775 | $105,701 – $201,750 | $105,701 – $201,775 |
| 32% | $403,551 – $512,450 | $201,776 – $256,225 | $201,751 – $256,200 | $201,776 – $256,225 |
| 35% | $512,451 – $768,700 | $256,226 – $640,600 | $256,201 – $640,600 | $256,226 – $384,350 |
| 37% | > $768,700 | > $640,600 | > $640,600 | > $384,350 |
2. Medicare IRMAA Surcharge Model (Age 65+)
| IRMAA Tier | Single / HoH / MFS MAGI | MFJ MAGI Threshold | Annual Surcharge / Person |
|---|---|---|---|
| Standard Tier | ≤ $109,000 | ≤ $218,000 | $0 / yr |
| Tier 1 | $109,001 - $137,000 | $218,001 - $274,000 | +$1,150 / yr |
| Tier 2 | $137,001 - $171,000 | $274,001 - $342,000 | +$2,890 / yr |
| Tier 3 | $171,001 - $205,000 | $342,001 - $410,000 | +$4,620 / yr |
| Tier 4 | $205,001 - $500,000 | $410,001 - $750,000 | +$6,360 / yr |
| Tier 5 (Max) | > $500,000 | > $750,000 | +$6,940 / yr |
IRC §72(t) SEPP, Roth Ladders & Social Security
IRC §72(t) SEPP Distribution Schedules
Under IRC §72(t)(2)(A)(iv), individuals retiring before age 59½ can tap pre-tax Traditional IRAs and 401(k)s completely free of the 10% IRS early distribution penalty through Substantially Equal Periodic Payments (SEPP).
- The 5-Year / Age 59½ Rule: Distributions must continue without modification for 5 full years or until the participant reaches age 59½ (
max(startAge + 5, 60)), whichever is longer. Busting the plan triggers retroactive 10% penalties plus interest. - IRS Notice 2022-6 Methods: Supports Fixed Amortization (using a statutory interest rate floor of 5.0% and Treas. Reg. §1.401(a)(9)-9 Single Life Expectancy) and the annual RMD method.
- Account Carve-Out: Segregate a designated balance rather than subjecting an entire portfolio to mandatory fixed distributions.
Roth Conversion Ladders & 5-Year Aging
Moving pre-tax balances into Roth IRAs during lower-income gap years allows retirees to permanently shield future growth from RMDs and taxes.
- 5-Year Seasoning Rule: Under Treasury Reg. §1.408A-6, each converted tranche must age for 5 tax years before the converted principal can be withdrawn tax- and penalty-free prior to age 59½.
- Dedicated Wizard: Configure target brackets (Fill 10%, 12%, 22%, 24%), ACA 400% FPL limits, or custom dollar conversions directly inside the Events tab.
- Tax Optimizer Integration: 1-click "Apply to Plan" automatically schedules and activates the optimal ladder parameters.
Adverse Policy Cliffs & Diagnostic Alerting
Retirement decumulation is riddled with sharp, non-linear policy thresholds where crossing an income boundary by even $1.00 triggers disproportionate financial penalties, lost subsidies, or surcharges. The FNC Retirement Engine provides proactive, multi-layer awareness to prevent accidental cliff breaches.
Medicare Part B and Part D premiums are subject to Income-Related Monthly Adjustment Amounts (IRMAA) based on your Modified Adjusted Gross Income (MAGI) with a 2-year lookback ($t-2$).
• Cliff Mechanic: Exceeding a bracket boundary (e.g. $218,000 for MFJ or $109,000 for Single) by $1 triggers the full surcharge tier ($1,150 to $6,940/year per covered spouse).
• Independent Age Tracking: Surcharges only apply for the spouse who has attained age 65.
For early retirees purchasing private coverage through the ACA marketplace under standard 2026 statutory rules (IRC §36B):
• The 400% FPL Hard Cliff: While income between 100% and 400% FPL qualifies for premium tax credits capping health costs at 2.0%–8.5% of income, exceeding 400% FPL immediately eliminates all subsidies.
• Financial Impact: A single dollar of excess income can trigger an immediate out-of-pocket loss of $12,000 to $24,000+ per year in SLCSP benchmark premiums.
Withdrawing funds from Traditional tax-deferred accounts prior to age 59½ without qualifying for an IRC §72(t) SEPP schedule triggers a statutory 10% IRS penalty.
• Roth Ordering Rules: Under Treasury Reg. §1.408A-6, taxable Roth conversion tranches withdrawn prior to completing the 5-year aging seasoning period are also subject to this 10% early distribution penalty.
The engine actively surfaces these adverse events across the entire application:
• Header KPI Pill (kpi-cliffs-status): Displays clean shield or numeric active cliff count with an expansive hover breakdown tooltip; clicking jumps directly to the Data Audit Table.
• Tax Optimizer Warning Box: Prominently featured at the top of the Tax Optimizer tab when risks are detected, summarizing total cliff penalties, lost ACA subsidies, and actionable mitigation tips.
• Audit Table "Cliffs & Alerts" Column: Color-coded badges with hover tooltips displaying the exact dollar penalty and cliff type for each simulated calendar year, paired with distinct row styling for ACA breaches and IRMAA surcharges.
Accumulation Phase Event Income Allocation
When positive cash flow life events occur during your working years (such as inheritances, business exits, equity vesting, or side income bonuses), the engine ensures these funds are productively invested rather than remaining idle as uninvested cash.
If your plan specifies annual savings additions in the sidebar, event income is distributed pro-rata across Taxable Brokerage, Tax-Deferred, Roth IRA, and Cash matching your active savings strategy proportions.
The engine checks remaining room under IRS statutory limits ($23,500 401(k), $7,000 IRA, age 50 catch-up, and SECURE 2.0 super catch-up). Any excess event dollars allocated to tax-advantaged accounts automatically overflow into the Taxable Brokerage account and update your cost basis.
If your baseline annual savings additions are all set to $0, the engine intelligently allocates the windfall according to your target asset allocation: the stock percentage (stockAlloc) goes into Taxable Brokerage, and the remainder goes into Cash.
Decumulation Strategies, Guardrails & Income Isolation
The FNC Retirement Engine supports six distinct withdrawal algorithms, each dynamically adjusting annual distributions in response to portfolio performance, inflation, and remaining longevity. Crucially, non-portfolio guaranteed income (Social Security, pensions, annuities) is cleanly isolated to eliminate artificial spending cuts and false Monte Carlo failures.
Guyton-Klinger rules dynamically protect portfolio longevity while harvesting market upside:
• Capital Preservation Cut: If the current withdrawal rate exceeds 1.2× the initial rate, spending is trimmed by 10%. (Sunsets when retirement horizon ≤ 15 years).
• Prosperity Bonus: If the withdrawal rate falls below 0.8× the initial rate, spending is boosted by 10%.
• Inflation Rule: Skips inflation adjustments following a negative market return if the current rate exceeds the initial rate.
• Income Event Isolation: The withdrawal rate is monitored strictly against net portfolio demand (Math.max(0, desiredLiving - evIncome)) rather than gross budget. Guaranteed income (Social Security/pensions) reduces required portfolio draws without triggering false cuts, and guardrails re-anchor when guaranteed income commences.
• Vanguard Dynamic Spending: Draws a baseline percentage (e.g. 4.5% of net worth), constrained within a -2.5% cut floor and a +5.0% raise ceiling relative to prior year spending.
• Variable Percentage Withdrawal (VPW): Actuarially calculates distribution percentage from asset allocation and remaining horizon (endAge - age + 1). Systematically exhausts portfolio at final age while preventing premature depletion.
• Fixed Percentage: Liquidates a fixed % (e.g. 4.0%) of start-of-year wealth annually, fluctuating directly with market returns.
• Hebeler Autopilot: Blends 50% RMD-based drawdown with 50% prior year inflation-adjusted spending.
• Additive Guaranteed Income: For all percentage models, guaranteed income is additive (portDraw + evIncome), maintaining household lifestyle.
mcSuccessFloor)
Under correlated Markov-switching Monte Carlo simulation (1,000 to 5,000 trials sampling equity volatility, bond yield shocks, and inflation shifts):
• Success Definition: A trial is deemed successful if (1) no portfolio or tax shortfalls occur (shortfall === false and carry-forward tax deficit ≤ $1.00), and (2) delivered spending (portfolio draws + guaranteed income events) never falls below the user's defined MC Success Floor (default 80%) relative to baseline living standard in any year of retirement.
• Distinct Strategy Rates: Because dynamic strategies adjust distributions to market conditions rather than blindly taking fixed draws, they produce distinct, strategy-appropriate success rates and risk/reward trade-offs.
1-Page Retirement Blueprint, Visual Timeline & COLA Modeling
Retirement planning requires both microscopic technical auditability and executive clarity. Version 4.3 introduces premier visual presentation tools that bridge forensic tax modeling with intuitive, single-sheet decision making.
• Executive One-Pager: Distills 50 years of complex simulations into a single-sheet overview designed for spousal review and advisor check-ins. Accessible via the Export/Import popup.
• 5 Core Plan Quadrants: Highlights the Executive Verdict (readiness, FI age, MC confidence), 3-Bucket Asset Architecture (Taxable, Pre-tax, Roth, Cash), Lifecycle Roadmap, Tax Strategy & Cliff Watch, and an immediate 4-bullet Year 1 Action Checklist.
• Dedicated Print Engine: Formatted specifically via body.blueprint-print-active to fit perfectly onto exactly one 8.5×11" or A4 sheet with zero multi-page table overflow.
• Unified Trajectory Placement: Merges lifecycle stage bands and SWR FI Milestones (Lean, Target, Fat SWR thresholds) right above the Net Worth Trajectory chart.
• Staggered 2-Tier Anti-Overlap Pins: Distributes milestones across Upper (top: 0px) and Lower (top: 28px) tiers with vertical connecting ticks, eliminating label overlap between adjacent gates (59½, 60/Retire, 65/Medicare, SS, RMD).
• Interactive Popovers: Hovering any milestone badge reveals an explanatory popover detailing statutory rationale and precise dollar amounts.
• 1-Click Quick Templates: Pre-populates common life milestones directly into the modal: + Pension ($24k/yr, taxable, COLA), + Inheritance ($100k lump-sum, non-taxable), + College Tuition ($25k/yr expense), and + Home Sale ($150k proceeds).
• Inflows vs. Outflows Grouping: Organizes active life events into distinct Guaranteed Inflows (emerald) and Expense Outflows (rose) sections with running item counts.
• Selective Indexing: Individual life events feature an explicit [x] Adjust for Inflation (COLA) toggle.
• Indexed vs. Flat Cash Flows: Social Security naturally increases with inflation. In contrast, fixed private pensions, level annuities, fixed mortgages, or debt obligations do not.
• Purchasing Power Erosion: When COLA is disabled (cola: false), nominal cash flows remain strictly flat, accurately capturing real-dollar purchasing power decay over a 30-year retirement.