Tax Loss Harvesting Calculator — 2026 Federal Estimate

Tax-loss harvesting is a planning strategy in which an investor considers realizing a capital loss so it can enter the tax netting process. The tax result and the investment decision are separate: a tax benefit does not establish that selling is prudent.

This calculator compares a current scenario with a scenario that assumes only the checked positions are sold. It does not choose investments, recommend trades, or model how the portfolio behaves after a sale.

A market-price decline by itself is generally an unrealized loss and does not enter the capital-loss calculation. A loss usually requires a completed sale or exchange and an allowed tax loss based on amount realized and adjusted basis.

The calculator treats the proposed sale as completed only inside the submitted harvest scenario. Actual deductibility can still depend on basis, wash-sale rules, asset classification, and other return facts.

A capital asset held one year or less is generally short term; one held more than one year is generally long term. The user supplies that classification because TaxArith does not determine acquisition dates, holding-period adjustments, or special rules.

Final net short-term gain is taxed as ordinary income. Final net long-term gain can share the preferential 0%, 15%, and 20% stack with qualified dividends.

The model first combines gains, current losses, entering carryover, and allowed harvested loss inside each holding-period category. It does not collapse short-term and long-term activity into one number at the start.

Only after those separate results are known do opposite-signed short-term and long-term amounts offset. That ordering determines whether a remaining gain is ordinary or preferential and which loss character can carry forward.

Short-term losses first reduce short-term gains, while long-term losses first reduce long-term gains. An entering carryover retains its character and is included in its matching category.

The modeled allocation treats pre-existing activity first and then adds the newly harvested loss, making the use of harvested loss consistent and reproducible without claiming official lot-level attribution.

If one category has a gain and the other a loss, the opposite results offset. A $10,000 short-term gain and $6,000 long-term loss leave a $4,000 short-term gain; an $8,000 short-term loss and $3,000 long-term gain leave a $5,000 short-term loss.

Equal and opposite amounts leave no net gain or loss. If both categories remain losses, both characters are preserved for the deduction and carryforward steps.

For Single, Married Filing Jointly, Head of Household, and Qualifying Surviving Spouse, the modeled annual deduction is limited to $3,000 of remaining net capital loss and available ordinary taxable income.

This is an income deduction, not a $3,000 tax credit. The tax reduction depends on the full federal tax calculation and can be zero even when a loss exists.

Married Filing Separately uses a $1,500 annual capital-loss deduction limit in this model. Other supported filing statuses use $3,000.

The submitted filing status also selects the applicable ordinary brackets and preferential income thresholds for both scenarios.

A net capital loss not used against gains or as the current-year deduction may carry forward. This estimate displays the unused short-term and long-term amounts separately.

The official amount can depend on the Schedule D Capital Loss Carryover Worksheet, taxable-income limitations, and other return items not modeled here.

A short-term carryover remains short term and a long-term carryover remains long term. Enter each amount from the prior return or applicable worksheet rather than trying to infer both characters from one total loss.

After cross-netting, the model uses remaining short-term loss first for the annual deduction and preserves the character of any amount still unused.

A short-term loss can offset short-term gain that would otherwise be taxed through ordinary brackets. In some circumstances that produces a larger current-year tax effect than offsetting long-term gain taxed at a preferential rate.

That is not guaranteed: existing losses, income level, qualified dividends, the annual deduction limit, and the regular-tax safeguard all affect the comparison.

Qualified dividends are included once in taxable income and remain identical in the current and harvest scenarios. They do not participate in capital gain-and-loss netting.

They share the preferential income stack with final net long-term gain. The shared tax engine limits preferential income to final taxable income and compares the preferential method with regular tax.

A wash sale can disallow some or all of a loss when stock or securities are sold at a loss and substantially identical property is acquired within the applicable period. The calculator subtracts only the disallowed amount entered by the user.

It does not determine whether two assets are substantially identical or search transactions. A risk selection is a review flag, not a legal conclusion.

The wash-sale window includes the 30 days before the loss sale and the 30 days after it, in addition to the sale date. A replacement purchase made before a planned sale can therefore matter.

Repeated purchases, dividend reinvestments, employee plans, and trades in other accounts can create facts that need review even when no purchase is planned after the sale.

Substantially identical is a facts-and-circumstances concept. Similar economic exposure alone does not let this calculator reach a reliable classification, and the name or ticker alone may not resolve the question.

TaxArith asks the user to enter a disallowed amount already determined independently. Consult current IRS guidance and a qualified professional for uncertain replacements.

Using a different brokerage account does not necessarily remove wash-sale risk. Broker reporting may identify only a subset of the transactions relevant to a taxpayer.

The calculator does not connect to brokers or reconcile accounts, so the submitted answers must reflect the user’s own cross-account review.

A spouse’s acquisition can be relevant to a wash-sale analysis. The security-specific prompt flags that possibility but does not inspect a spouse’s transactions.

A zero warning count means only that the submitted fields did not flag a fact; it is not confirmation that no spouse-related issue exists.

Acquisition in an IRA or Roth IRA can matter and can have consequences different from a taxable-account replacement purchase. Do not assume every disallowed loss simply increases basis in that situation.

TaxArith does not inspect retirement accounts, determine the consequence, or calculate replacement basis.

A wash-sale adjustment can apply to only part of a position’s potential loss. The entered disallowed amount is capped at the potential loss, and the remainder is the allowed harvested loss.

Share matching and partial replacement analysis happen outside this calculator. Enter the resulting dollar amount rather than a percentage.

A disallowed wash-sale loss is generally added to the basis of replacement stock or securities and may affect its holding period. Acquisitions in an IRA or Roth IRA can have different consequences.

The model stops at the entered current disallowance. It does not compute replacement-asset basis, holding period, or a future sale.

Current IRS guidance generally describes wash-sale rules for stock or securities. An ordinary digital asset should not automatically be classified as a security, while a tokenized stock or security may fall within those rules.

The calculator does not determine digital-asset classification and does not promise that a crypto transaction avoids wash-sale or other anti-abuse rules.

The model subtracts estimated selling costs from gross proceeds, never below zero, to determine net sale proceeds. Potential loss is adjusted basis minus those net proceeds, never below zero.

Basis can require adjustments for prior wash sales, reinvestments, gifts, inheritance, corporate actions, and other facts. The user must supply an independently supported adjusted basis.

A position can show a paper loss while it is still held, but that decline is not included in the current scenario. The harvest scenario treats only selected rows as proposed sales.

If the estimated basis is equal to or below net sale proceeds, the selected row fails validation because it does not currently create a modeled loss.

Estimated tax savings compare two modeled current-year federal tax amounts. They do not include the investment’s economic loss, future appreciation, transaction spreads, replacement costs, or future taxes.

A smaller tax bill does not make the overall trade profitable, and deferred loss can produce no current-year tax savings.

Selling can change asset exposure, diversification, risk, voting rights, and participation in a market rebound. Waiting to repurchase can also create tracking differences and market-movement risk.

These investment consequences are outside the federal tax comparison. The calculator does not recommend a replacement security or rebalancing action.

Common records include trade confirmations, brokerage statements, Forms 1099-B or 1099-DA as applicable, acquisition history, basis adjustments, fee records, and prior Schedule D carryover worksheets.

Form 8949 and Schedule D may still be required. TaxArith does not prepare either form or reconcile broker-reported and taxpayer-adjusted amounts.

The federal capital-gain and capital-loss netting rules, the $3,000 annual limit, the $1,500 Married Filing Separately limit, carryover character, and wash-sale guidance were reviewed on August 11, 2026 using IRS Topic No. 409, Publication 550, the available Schedule D instructions, Form 8949 guidance, and current IRS digital-asset guidance.

This is a planning model. It does not replace Form 8949, Schedule D, the Capital Loss Carryover Worksheet, or advice based on the taxpayer’s complete return and investment circumstances.