Every formula, assumption, source, and limitation behind StockFocus calculators. We believe trust comes from transparency — read it, question it, then use the tools confidently. Last updated May 28, 2026.
Official primary sources only: IRS publications (Pub 590-B for RMDs, Rev. Proc. 2024-40 for 2025 brackets), SSA's official benefit formulas and 2025 COLA, CMS for 2025 Medicare Part B and IRMAA brackets, and the U.S. Census Bureau and OECD for life-expectancy assumptions. Every calculator section on this page lists its specific sources with links.
Every quarter, and immediately after major legislation. Last updated May 28, 2026 to incorporate the One Big Beautiful Bill (permanent 37% top rate, $6K/$12K Senior Bonus Deduction, $108K QCD limit, permanent ~$15M estate exemption).
We use 1,000 trials with historical real (inflation-adjusted) US stock and bond returns drawn from the standard parametric distributions used in academic retirement research. Results are illustrative, not predictive. We disclose the assumptions (return means, volatility, withdrawal timing) in the Will-My-Money-Last methodology section so you can stress-test them yourself.
We use the official 2025 CMS IRMAA brackets ($106,000 single / $212,000 MFJ thresholds and up) and apply both Part B and Part D surcharges. Some calculators only show Part B or use stale 2023/2024 brackets. We also model the cliff-distance warning, since IRMAA is a hard cliff not a phase-in.
No. All calculators run entirely in your browser. Nothing is sent to our servers and we have no analytics on the inputs themselves. You can verify this by opening your browser's network tab while you use any calculator.
Three big ones: (1) all calculators are general planning tools, not personalized advice — your situation may have factors we don't model (special needs trusts, business interests, foreign income). (2) Tax law changes after our last-updated date won't be reflected until our next quarterly refresh. (3) Monte Carlo results depend on assumed return distributions; real markets can deviate. Always cross-check with a fee-only fiduciary before making irreversible decisions.
Yes. This page is public and the source links are official. We recommend citing both this page and the underlying IRS/SSA/CMS source so your records remain defensible if rules change.