Every calculator on CeoCult is built to these six rules and every dispatch is verified against them. The Procedure is what separates a tax instrument from a marketing form.
We call this standard The CeoCult Self-Employed Tax Audit: IRS-sourced formulas, current to the active tax year, verified against the open data in our 75 Freelance & Self-Employment Tax Statistics study and checked with our seven free tax calculators. Authored and reviewed by Vincent Wesley Couey (ORCID). We do not publish tax advice under fabricated credentials. Our peer-archived, DOI-backed dataset: 1099-K Reporting Thresholds by State (DOI 10.5281/zenodo.20632600).
No "consult your tax professional" hedging where the rule is unambiguous. Where pro advice is genuinely needed (multi-state filings, $1M+ revenue, partnership/LLC structuring), we name the threshold and tell you to stop reading.
Tax code is hard. Tax outcomes for the typical freelancer aren't. We refuse the hedge that protects the publisher at the cost of the reader.
Every calculator's underlying formula is sourced from an IRS publication: Pub 505 (Tax Withholding and Estimated Tax), Pub 587 (Business Use of Home), Form 1040-ES instructions (Estimated Tax for Individuals), Sched SE (Self-Employment Tax). Publication number cited in each tool footer.
Where the IRS rule has known practitioner-side interpretation differences (Reasonable Salary on S-Corp; home-office "exclusive use" standard), we name them and link to the underlying authority.
Federal brackets indexed to Rev. Proc. 2024-40. State-specific brackets cross-referenced against each state's January-published tax table. Every January we run a full audit; date-stamped in each tool footer.
If you see a calculator on the internet still using 2024 brackets in 2026, that calculator was never going to help you.
Every calculation runs in your browser. Your inputs never leave your device. No server-side endpoint. No analytics on tool pages. No third-party scripts in the calculation flow. The JS is auditable, view source, run it offline, fork it.
Tax inputs are the kind of personal data that should never leave the device. We treat that as binding, not as a marketing feature.
Every instrument ships responsive and touch-friendly. Real iOS + Android device passes before publish, not just dev-tools emulation. Calculators with sliders, multi-step forms, and result tables all hit a finger-friendly threshold (44px tap targets).
Most self-employed people do their first set-aside math on the phone after a deposit hits. The calculator has to work there.
Underpayment penalty rules: pay 110% of prior-year tax liability (for AGI > $150K), or 90% of current-year liability, or owe less than $1,000 at filing. The instruments default to safe-harbor calculation, we don't make underpayment penalty avoidance an upsell.
This is the rule most quarterly-estimated-tax content gets wrong, and the one that costs freelancers actual money when they get it wrong.
Every calculator and dispatch cites its IRS source. Below is the standing reference set used across all instruments on the site, refreshed each January.
"The publication number is the price of admission."