When engineering client-side financial calculators for high-tax US East Coast jurisdictions (New York City, New Jersey, Massachusetts, Connecticut, and Pennsylvania), flat national estimators fail because statutory tax codes operate on discrete exemptions, supplemental withholding cliffs, and non-linear netting rules.
In this quantitative engineering breakdown from the East Corp Capital Quantitative Desk, we document four open-source deterministic algorithms and visual reference matrices for the 2026 tax and commercial underwriting year.
1. Fixed-Income Tax Arbitrage: 31 U.S.C. § 3124 (US Treasury Bills vs. Bank CDs)
Under 31 U.S.C. § 3124(a), interest income from direct United States Treasury obligations (4-week to 52-week T-Bills, T-Notes, and TIPS) is 100% exempt from state and municipal income taxes. Conversely, commercial bank CDs and High-Yield Savings Accounts (HYSAs) face combined state and city rates up to 14.776% in New York City (10.90% NYS + 3.876% NYC), 10.75% in New Jersey, and 9.00% in Massachusetts.
function computeTaxEquivalentCdYield(tBillRate, fedMarginalRate, stateLocalRate) {
const netTbillAfterTax = tBillRate * (1 - fedMarginalRate);
const effectiveCombinedRetention = 1 - fedMarginalRate - stateLocalRate;
const cdEquivalentApy = netTbillAfterTax / effectiveCombinedRetention;
return {
netTbillYieldPct: Number((netTbillAfterTax * 100).toFixed(3)),
cdEquivalentApyPct: Number((cdEquivalentApy * 100).toFixed(3))
};
}
- Live Interactive Engine: 2026 US Treasury Bills vs. Bank CDs After-Tax Yield Calculator (NY, NYC, NJ, MA & CT)
- Standalone Simulator: T-Bills vs. CD Tax-Equivalent Yield Simulator
2. Wall Street & Executive Supplemental Payroll Withholding (26 C.F.R. § 31.3402(g)-1 & NYS-50)
When a New York City employer disburses a cash bonus, commission, or RSU vest, payroll engines apply mandatory supplemental flat rates rather than progressive W-4 tables:
- Federal IRS Supplemental Rate: 22.00% up to $1,000,000; 37.00% mandatory above $1,000,000.
- New York State Supplemental Rate (Publication NYS-50): 11.70% mandatory withholding.
New York City Resident Supplemental Rate: 4.25% mandatory withholding.
Live Interactive Engine: 2026 NYC & NY State Supplemental Bonus Tax Withholding Calculator
Refund Tracker & Form IT-201 Reconciliation: New York State & NYC 2026 Tax Refund Schedule Tracker
3. IRC § 1031 Like-Kind Exchange Boot & 25% § 1250 Depreciation Recapture
Under Treas. Reg. § 1.1031(d)-2 and IRS Form 8824, Cash Boot received from escrow cannot be offset by assuming additional mortgage debt, whereas Mortgage Boot (net debt relief) can be offset by contributing fresh cash at closing.
- Live Interactive Engine: 2026 IRC § 1031 Exchange Boot & 25% Depreciation Recapture Calculator
- DST 1031 & 45/180-Day Deadlines: Delaware Statutory Trust (DST) & 1031 Reverse Exchange Simulator
4. SBA 7(a) & 504 Commercial Loan DSCR Underwriting (SOP 50 10 7.1)
- SBA 7(a) & 504 Simulator: 2026 SBA Business Loan Payment, Guaranty Fee & DSCR Calculator
- Commercial Real CRE DSCR: Cap Rate, Cash-on-Cash & DSCR Loan Calculator
- Open-Access Embeddable Widgets (?embed=1): 60 Free CC BY 4.0 Financial Calculators
Top comments (0)