How the Biden's Tax Plan Calculator works
This tool compares your federal income tax under current 2024 law with the tax you would owe under the individual income tax provisions Biden's administration has proposed in successive budgets. It is not a calculator of enacted law — no version of this plan has passed Congress — but a way to see the mechanical effect of the two provisions most consistently proposed: a higher top marginal rate above $400,000/$450,000, and a Social Security payroll tax reapplied to high wages.
The two provisions modeled
1. Restoring the 39.6% top rate. The Tax Cuts and Jobs Act (TCJA) cut the top individual rate from 39.6% to 37% starting in 2018. Biden's budget proposals call for reverting that top rate to 39.6% for taxable income above $400,000 (single filers) or $450,000 (married filing jointly). Below that threshold, the current-law 2024 brackets (10%, 12%, 22%, 24%, 32%, 35%) are unchanged — the plan is designed so households under $400,000 see no federal income tax increase.
2. Reapplying Social Security tax above $400,000. Social Security (OASDI) payroll tax is 12.4% of wages, split 6.2%/6.2% between employee and employer for W-2 workers or paid in full by the self-employed, but only up to an annual wage base ($168,600 in 2024). Biden's proposal leaves the tax off wages between the wage base and $400,000 (a "donut hole") but reimposes the same rate on every dollar earned above $400,000.
The formula
For taxable income I and threshold T ($400,000 single / $450,000 joint):
Current-law tax = sum of I taxed through the ordinary 2024 progressive brackets (10% through 37%).
Biden-plan tax = tax on min(I, T) through the ordinary brackets, plus 39.6% × max(0, I − T).
Added Social Security tax = payroll rate × max(0, wages − $400,000), where the payroll rate is 6.2% for W-2 employees (the employee's own share) or 12.4% for the self-employed.
Worked example
A single filer with $500,000 of taxable income and $500,000 of wages: current-law tax on $500,000 through the 2024 single brackets is $145,374.75. Under the Biden plan, the first $400,000 is taxed the same way ($110,374.75), and the remaining $100,000 is taxed at 39.6% ($39,600), for a plan total of $149,974.75 — $4,600 more, which is exactly the 4.6 percentage-point rate difference (39.6% − 35%) applied to that last $100,000. As a W-2 employee, the added Social Security tax on the $100,000 of wages above $400,000 is 6.2% × $100,000 = $6,200. The combined estimated increase is $10,800.
What this calculator does not include
- State and local income tax, which is unaffected by federal proposals and must be added separately.
- Capital gains and corporate tax changes — Biden's broader proposals also include taxing long-term capital gains as ordinary income above $1 million and raising the corporate rate, but those apply to different income types and are not modeled here.
- Deductions, credits, and AMT — this calculator works directly from taxable income; it does not model the standard deduction, itemized deductions, or the alternative minimum tax.
When to re-run this calculation
Re-run whenever your taxable income, filing status, or wage income changes materially, or when a new legislative proposal changes the threshold or rate. Because none of this is enacted law, treat the output as a policy-impact estimate, not a tax filing figure.