This page documents the exact mathematical formulas, statutory tax brackets, and official data feeds powering the East Corp Capital Macroeconomic Observatory and our 12 Interactive Financial Calculators.
1. Federal, New York State & NYC Tax Computation Methodology
- Federal Income Tax & FICA: Models standard deductions ($15,000 Single / $30,000 Married Filing Jointly / $22,500 Head of Household), progressive marginal brackets (10% to 37%), Social Security OASDI tax (6.2% up to the $176,100 wage base), Medicare Hospital Insurance tax (1.45% on all wages), and the 0.9% Additional Medicare Tax above $200,000 ($250,000 MFJ).
- New York State (Form IT-201 / IT-203): Applies NYS standard deductions ($8,000 Single / $16,050 MFJ) and progressive tax brackets from 4.00% up to 10.90%.
- New York City Resident Tax & Yonkers Surcharge: Applies the four NYC resident brackets (3.078%, 3.762%, 3.819%, and 3.876%) for residents of Manhattan, Brooklyn, Queens, the Bronx, and Staten Island, or the 16.75% resident tax surcharge for Yonkers.
2. NYC Real Estate Closing Cost & Mansion Tax Formulas
- Progressive NYC Mansion Tax (NYS Tax Law § 1402-a): Applies all 8 statutory tiers starting at 1.00% ($1.0M–$1.999M), 1.25% ($2M–$2.999M), 1.50% ($3M–$4.999M), 2.25% ($5M–$9.999M), 3.25% ($10M–$14.999M), 3.50% ($15M–$19.999M), 3.75% ($20M–$24.999M), and 3.90% ($25M+).
- NYC Mortgage Recording Tax (MRT): Applies 1.80% (net of $30 deduction) on Condo/Townhouse mortgages under $500,000 and 1.925% on mortgages of $500,000 or more. Co-op share loans are exempt ($0 MRT).
3. US Treasury Bills vs. Bank CDs Tax-Equivalent Yield Formula
Because U.S. Treasury interest is exempt from state and local income taxes under 31 U.S.C. § 3124, we compute the Tax-Equivalent CD APY required to match a Treasury Bill yield as:
Tax-Equivalent CD APY = T-Bill Yield × (1 − Federal Marginal Rate) ÷ (1 − Federal Marginal Rate − State/Local Marginal Rate)