§ 01
Who We Are
A free tax-calculator suite for US tech workers with equity compensation. Eight live calculators, twenty-three blog guides, and a unit-tested calc layer. Every claim cites an IRC section or IRS publication. Built by one indie dev — Earth — with the discipline of a small audit firm and the build cadence of a solo engineer.
8
Live calculators
23
Blog guides
446
Unit tests
100%
Cited claims
Calculator coverage: RSU, ISO/AMT, ESPP, NSO, Bonus, Quarterly Safe Harbor, AMT Credit Recovery, State Stock-Comp.
§ 02
Audience
US W-2 employees with equity compensation. Mostly mobile, mostly anxious, mostly underserved by generic tax tools. They arrive after a vest, a payroll surprise, or a CPA invoice they didn’t expect.
- Income Median household $150K–$500K
- Employer Public & late-stage private tech, W-2 with RSU/ISO/ESPP
- Peaks Post-vest panic · Q1 Year-end · Nov–Dec ESPP sale ISO exercise
- Device Mobile-first; reads on phone, executes on laptop
§ 03
Trust Signals
YMYL discipline
446 unit tests
CI-gated; bracket edges, AMT crossover, and wash-sale paths all covered.
Every calc cites IRC
Inline citations to IRC §§ and IRS Pubs on every result — no hand-waving.
Pure functional math
lib/tax is side-effect free. Deterministic, auditable, diff-able.
Versioned brackets
Constants pinned per tax year in git. TY2024, TY2025, TY2026 all reproducible.
YMYL discipline
“Pending CPA review” byline today; credentialed reviewer engaged when revenue justifies.
§ 04
What We Want From Partners
Affiliate · Direct · Hybrid
The ask
Whitelisted CPA & tax-prep affiliate links at the end of the RSU shortfall results panel and inside high-intent blog posts.
Example placement: bottom of the /calculators/rsu-shortfall results card, and inline in posts like estimated-tax-after-rsu-vest. The reader has just seen the size of the problem — they are looking for a next step.
-
01
FTC-compliant disclosure. Inline on every card. Never buried in a footer.
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02
Per-click or per-acquisition payouts accepted. Open to flat, CPL, CPA, or hybrid.
-
03
Direct partnership preferred over affiliate network when feasible. Network is fine as a starting point.
§ 05
The Surface Area
3 of 8 calculators shown
mathstub.com/rsu-shortfall
RSU Shortfall
IRC §83
Vest FMV$184,200
Withheld (22%)$40,524
Marginal bracket37%
Estimated shortfall
−$27,630
Owed at filing. Consider a Q4 estimated payment — IRC §6654.
mathstub.com/iso-amt
ISO / AMT
IRC §55, §422
Exercised shares12,000
Bargain element$312,000
AMT due
$73,840
Crossover hit at exercise. Track basis for AMT Credit Recovery in future years.
mathstub.com/quarterly
Quarterly Safe Harbor
IRC §6654(d)
Prior-year tax$94,210
110% safe harbor$103,631
YTD withheld$81,400
Status
Safe ✓
$5,558/quarter through Q4 keeps you inside the 110% rule. No underpayment penalty.