Why do I have to enter the threshold?

Thresholds change by year and filing status. Entering your guardrail keeps the tool evergreen and makes you decide intentionally.

Does this include NIIT or state tax?

Only if you model it via your rates. This tool focuses on headroom and tier splitting; final tax depends on your full return.

What if part of my gain is short-term?

Short-term gains are taxed differently. Use this for long-term gain planning only, and ask your CPA if the mix matters.

Capital Gains Headroom Calculator (User-Entered Guardrails)

Why This Tool Exists

Capital gains harvesting is not a vibe. It is a guardrails problem.

This tool helps you translate your baseline taxable income and your chosen threshold into a headroom number, then shows how a planned sale splits across tiers.

Execution note: Run the tool, then write down your assumptions and keep the receipts and logs as you go. The strategy that wins on paper only matters if your process holds up in the real world.

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Calculator How To Use This Tool Execution Notes FAQ

Baseline taxable income (before LTCG)

Use a conservative estimate from a projection or last year. This is taxable income, not gross.

Guardrail threshold (user-entered)

Enter the boundary you care about (thresholds vary by year and filing status).

Buffer under threshold

Dividends and income surprises happen. Buffer keeps the plan stable.

Planned long-term capital gain

Optional: lower-tier tax rate (%)

If you want a dollar estimate, enter the rate you expect to apply inside the guardrail.

Optional: higher-tier tax rate (%)

Enter the rate you expect to apply above the guardrail. Include state if desired.

Headroom (after buffer)

Threshold minus baseline minus buffer

Planned inside guardrail

Lower tier portion

Planned above guardrail

Higher tier portion

Component	Amount	Tax estimate

Headroom is only useful if your baseline is honest. If you are near the line, buffer aggressively and re-run the tool before you execute the sale.

How To Use This Tool

Enter your baseline taxable income before long-term capital gains.

Enter the guardrail threshold you want to stay under (thresholds vary by year and filing status, so you control the input).

Enter your planned long-term capital gain and a buffer. The tool shows how much is inside vs above the guardrail.

Execution Notes

If you are near the line, use a buffer. Small surprises happen: dividends, interest, bonuses, and business income shifts.

Save a dated projection snapshot with the tool output so you can explain your decision later.

Use conservative numbers. Optimism is how people accidentally spill into the next tier.

Documentation Checklist (Keep It Defensible)

Create a one-page objective memo before you execute (what outcome you are trying to buy).
Store your assumptions and calculations in a dated PDF (no year-end reconstructions).
Keep evidence in the same folder structure every month (receipts, logs, approvals).
Ask your CPA what would make this easy to sign off on, then build that packet.

Primary Sources To Verify Before You Act

Use primary guidance and your own records before you treat any page like a final answer. These are the source layers that should drive the decision.

Current IRS forms, instructions, and publications for the relevant tax year
Your actual account statements, payroll reports, entity records, and advisor memos

Capital Gains Headroom Calculator (User-Entered Guardrails)

Why This Tool Exists