Methodology

Purpose

These pages are a public demonstration of what an investment adviser representative looks at and computes before advising a client: the intersection of tax and investing at the level a planning firm works at (equity compensation, bracket management, concentration), built so that every number is deterministic, sourced and reproducible. There are no clients, no logins and nothing is stored; the sample household is synthetic.

The deterministic-math principle and how it is enforced

Every displayed number is the output of a pure function in assets/js/calc/. Those modules take the parameter file explicitly, import no DOM or network code, and never read the clock. Page code formats and displays; it never computes. This is enforced, not promised:

• Parameter provenance. Every numeric leaf in the tax-parameter file carries value, source, url and retrieved. A build script walks the file and fails on any leaf without all four, on any bracket table that is not strictly increasing, and on any rate outside [0, 1]. The browser loader runs the same validation before a page renders.
• No hardcoded numbers. A second build script fails on any numeric literal in the calc modules other than 0, 1, 2, 12, 100 and loop bounds; the pseudo-random generator's algorithm constants are the only annotated exceptions.
• Tests. Every calc module has unit tests with hand-checked golden cases (the arithmetic is written out in the fixture), the test cases listed in the specification, and property tests (tax non-decreasing in income, AMT non-decreasing in shares, concentration non-increasing across a schedule) over a seeded grid. Every action-queue rule has a fires / does-not-fire pair. The publisher has recorded-fixture tests. A headless-browser suite loads every page and checks that it renders, validates, syncs its inputs to the link, and uses no storage.
• Show the math. Every tool renders its intermediate values with the formula each came from, in the order computed. The symbolic formulas below are rendered from the same text the tool pages use, so they cannot drift.
• Nothing unverified ships. Where a parameter or data point could not be sourced, the page shows "not available" rather than a placeholder. The parameter table lists the retrieval date of every value.

Formulas

Tax parameters

Notes recorded with the file

Market data sources and attribution

The dashboard's market strip reads a snapshot published once each weekday evening by a small machine at home that fetches public series from FRED (Federal Reserve Bank of St. Louis) and writes one JSON file to object storage. The site never talks to that machine. If any required series is missing or stale the publisher keeps the previous file and logs the failure; the page shows an "as of" badge after five days and "market data unavailable" if the file cannot be read.

• Treasury yields (DGS3MO, DGS2, DGS10, DGS30), the 10-year real yield (DFII10) and the federal funds target range (DFEDTARL, DFEDTARU): Board of Governors of the Federal Reserve System, via FRED.
• The 2s10s spread (T10Y2Y) and 10-year breakeven inflation (T10YIE): computed by the Federal Reserve Bank of St. Louis from Board data.
• CPI (CPIAUCSL) and unemployment (UNRATE): U.S. Bureau of Labor Statistics, via FRED. CPI year over year is the latest index divided by the same month a year earlier, minus one.
• 30-year mortgage rate: "Freddie Mac, 30-Year Fixed Rate Mortgage Average in the United States [MORTGAGE30US], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/MORTGAGE30US".
• Not shown: ICE BofA credit spreads (BAMLC0A0CM, BAMLH0A0HYM2) and the Cboe VIX (VIXCLS). Their FRED terms restrict redistribution to third parties without written approval, so the strip omits them; the translation rules that would use them stay dormant unless a series is present.
• Every tax rate in a translation line is computed through the calc modules at a stated reference profile (married filing jointly, $450,000 taxable income, in-state muni, NIIT on); none is typed into the text.

The economic-cycle reading is the existing cycle model's published snapshot, unchanged; see the cycle page.

Planning calendar

Known simplifications

• Federal and California ordinary brackets only. No credits, phase-outs, the qualified business income deduction, the SALT cap's interaction with itemizing, or the Social Security benefit-taxation thresholds.
• California 2026 brackets and standard deduction were not published when the parameter file was retrieved; the 2025 amounts are used and flagged. California taxable income is taken as the federal figure in every tool.
• AMT is simplified: the only adjustments are the standard deduction or SALT add-back and the ISO bargain element. No other preference items, no foreign tax credit interplay, no minimum tax credit carryforward, no disqualifying-disposition modelling.
• Tax-equivalent yield ignores de minimis and market-discount rules, AMT on private-activity bonds, credit risk, duration and call features.
• The RSU tool assumes the flat supplemental withholding method and the California stock/bonus rate, ignores Social Security already withheld by a second employer, and applies the federal safe harbor only.
• The Roth tool uses this year's IRMAA thresholds as a proxy for the year that will actually apply, ignores ACA credits, state residency changes and the five-year rules, and has no IRMAA schedule for married filing separately.
• The concentration tool holds the price flat unless told otherwise, ignores blackout changes, 10b5-1 mechanics and wash-sale interactions, keeps net worth outside the position constant, and treats harvested losses as clean long-term losses.
• The retirement tool uses one blended return, flat effective tax rates rather than the bracket engine, Social Security in today's dollars with a COLA equal to inflation, no healthcare or long-term-care shocks, no home equity, and independent lognormal annual returns, which understate fat tails and ignore mean reversion.
• The action queue's thresholds are illustrative settings in data/rules.json, not a firm's policy.

Change log

• 2026.1 (2026-09-12). Initial parameter file for tax year 2026: federal brackets, standard deduction, capital-gain thresholds and AMT amounts from Rev. Proc. 2025-32; supplemental withholding and FICA from Publication 15 (2026) and Topic 560; NIIT from Topic 559; safe harbor from Publication 505 (2026); Uniform Lifetime Table from Publication 590-B; IRMAA from the CMS 2026 Part B fact sheet; charitable limit from Publication 526; California 2025 rate schedules, standard deduction and Behavioral Health Services Tax from FTB; California supplemental withholding from EDD DE 231PS; California AMT from the 2025 Schedule P instructions; SDI from EDD; Medicare eligibility age from Medicare.gov.