• PENALTY
  • BREAKDOWN
  • SCENARIO
  • HUMAN

How to estimate 409A tax penalties with your AI

Connect your AI to the US Section 409A Impact Calculator to model tax risks. Your agent handles the math so you can focus on the equity strategy.

Ask AI about this page

Short answer

How do I calculate 409A tax penalties?

Give your AI the strike price, the current fair market value, and the employee's tax bracket. The agent uses the estimate_tax_penalty tool to calculate the specific tax hit and interest penalties. You'll get a full breakdown of the financial impact.

Tax impact outcomes.

Where every calculation lands.

The AI processes your equity data into these specific views.

PENALTY

Total tax hit

The AI calculates the immediate tax penalty and the additional interest owed under Section 409A. You get a single number representing the total cost.

BREAKDOWN

Component analysis

The agent splits the penalty into the base tax, the 20% penalty, and the applicable interest. This shows exactly where the money is going.

SCENARIO

What-if modeling

You can ask the AI to change the FMV or the strike price to see how different valuation gaps change the penalty. It updates the math instantly.

HUMAN

Legal review needed

The AI provides the math, but it doesn't provide legal or tax advice. You must take these results to a tax professional for final verification.

The workflow

What your AI does when the data arrives.

Your agent acts as the calculator, turning raw equity numbers into a risk assessment.

  1. Data ingestion

    The AI gathers the necessary variables like strike price, FMV, and tax rates from your prompt or uploaded files.

    estimate_tax_penalty

  2. Penalty math

    The agent applies the Section 409A formulas to determine the penalty percentage and interest accrual.

    estimate_tax_penalty

  3. Impact summary

    The AI organizes the results into a readable format, highlighting the total liability for the employee.

    estimate_tax_penalty

  4. Risk comparison

    The agent compares different valuation gaps to show how much the penalty scales with the FMV error.

    estimate_tax_penalty

Try it

Copy these to start.

Use these prompts to trigger the calculation immediately.

Starting points

Swap out the bracketed numbers with your actual equity data.

US 409A Impact Calculator Connector

You're all set. Choose your MCP client and follow the setup instructions.

Connector linkhttps://edge.vinkius.com/vk_preview_7ZkvoXpHa5AkS1CWLLy1OSbvo0tJVPsXFTYKHrXA/mcp

Claude Desktop

Follow the steps below to connect in seconds.

  1. 1In Claude Desktop, open Settings → Connectors.
  2. 2Click “Add custom connector” and paste the connector link above as the remote MCP server URL.
  3. 3Click Add and start a new chat — US 409A Impact Calculator capabilities are ready to use.
Configuration · claude_desktop_config.jsonCopy
{
  "mcpServers": {
    "us-section-409a-impact-calculator-mcp": {
      "url": "https://edge.vinkius.com/vk_preview_7ZkvoXpHa5AkS1CWLLy1OSbvo0tJVPsXFTYKHrXA/mcp"
    }
  }
}
Copy into chat04

  • Estimate the 409A penalty for an option with a $1.00 strike price and a $5.00 FMV at a 37% tax rate.

  • Run a 409A penalty calculation using the data in my spreadsheet.

  • How much is the penalty if the FMV is $10.00 but the strike price was set at $2.00?

  • Compare the tax penalties for a 20% FMV gap versus a 50% FMV gap.

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FAQ

How this task behaves

  • 01

    Does the AI provide official tax advice?

    No. The AI only performs the mathematical calculations based on the Section 409A formulas. You must consult a tax professional for legal compliance.

  • 02

    Can the AI file these penalties with the IRS?

    No. The AI is a calculation tool only. It cannot submit documents or interact with government agencies.

  • 03

    What data do I need to provide?

    You need the strike price, the fair market value (FMV), and the employee's marginal tax rate.

  • 04

    Can the AI change my actual tax filings?

    No. The AI has no access to your tax accounts or filing systems. It only generates estimates based on the numbers you provide.

  • 05

    Does it account for state taxes?

    The tool focuses on federal Section 409A penalties. You should manually add state-specific tax considerations.

  • More questions about US Section 409A Impact Calculator? The Connector page answers them. See everything the US Section 409A Impact Calculator Connector can do

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