Stock Loss Tax Calculator 2026

The calculator nets short-term gains and losses, nets long-term gains and losses, then combines the two results to estimate net capital gain or loss.

If the final result is a net loss, it applies the annual ordinary-income deduction cap based on filing status and computes potential carryforward loss.

It also estimates federal tax savings from the deductible portion by comparing ordinary income tax before and after the allowable deduction.

Why harvesting works

Harvesting works because realized losses can offset realized gains, reducing taxable net gains. When losses exceed gains, limited ordinary-income deduction and carryforward rules provide additional long-term planning value.

This turns portfolio drawdowns into potential tax assets, but the strategy must be balanced with your investment thesis and allocation targets.

The $3,000 deduction limit and carryforward

The annual ordinary-income offset limit is a common misunderstanding point. Large losses are not "lost" when above the annual cap; they can typically carry forward and be used in later years.

Keeping clean carryforward records is crucial, especially for active investors with frequent taxable transactions.

Avoiding common pitfalls

The wash-sale rule can disallow losses if you repurchase substantially identical positions within the restricted window. Transaction-level discipline and documentation matter.

Always evaluate after-tax strategy in context of risk, concentration, and diversification, not just immediate tax savings.