Crypto Tax-Loss Harvesting Before December 31: Know Your Lots First

What Tax-Loss Harvesting Means for Crypto Holders

Tax-loss harvesting for crypto means selling a digital asset at a loss to offset capital gains elsewhere on your return. To harvest losses correctly, you must know which specific purchase lots (or batches of coins bought at a specific time and price) have unrealized losses, and whether each lot has been held more than one year or less. The difference determines whether your loss offsets short-term or long-term gains.

What Is a Lot, and Why It Matters

A lot is a single purchase—a batch of coins you bought together. If you bought 0.5 BTC on January 10 at $35,000 per coin and another 0.5 BTC on June 15 at $40,000 per coin, you have two lots. They have different cost bases: $17,500 and $20,000.

When you sell crypto, the IRS doesn't assume you sold the oldest or newest batch first—you must specify which lot you're selling and how you're identifying it. Different exchanges track purchases differently, and if you've moved coins between wallets or platforms, your cost basis can scatter across records. Before December 31, you need a unified picture of every lot, its cost, and its current value.

Holding Period: The One-Year Rule

A digital asset held more than one year qualifies as a long-term capital asset. Held one year or less, it's short-term. The holding period determines the tax rate applied to gains, and it also determines how losses offset gains on your return.

Example: You bought 1 ETH on March 1, 2024, for $2,500. On November 15, 2025, it's worth $1,800. That's a $700 loss. Since you've held it less than one year (from March 2024 to March 2025 would be one year), any loss is short-term. You'd use it to offset short-term gains first.

A lot you held from December 10, 2023, to December 15, 2025, crosses the one-year threshold on December 10, 2024. If you sell on December 9, the loss is short-term; if you sell on December 10 or later, it's long-term. This timing matters, especially when harvesting on or near a threshold date.

Track Lots and Cost Basis Now

You'll need to pull transaction history from each exchange where you hold or held crypto. Most major platforms (Coinbase, Kraken, Crypto.com, Gemini, Robinhood) have a tax or statements section that lets you export a CSV of all transactions—buys, sells, deposits, withdrawals, and income events like staking rewards.

Steps:

1. Log into each exchange and locate the tax reports or transaction download section.
2. Export the full transaction history for each account (check if the export includes cost basis and whether the platform matched buys to sells).
3. Download any statements from self-custody wallets you use, or import addresses into a tracking tool.
4. List out each lot by date purchased, amount, cost at purchase, and current value.
5. Calculate unrealized gain or loss per lot.
6. Note the purchase date so you know the holding period for each lot.

For most crypto holders, a spreadsheet works. For accounts with more than a few dozen transactions, or if you trade across multiple platforms, using dedicated record-keeping software can save hours of reconciliation. Hodl1099 imports transaction CSVs from major exchanges, organizes them by lot, calculates cost basis under FIFO, LIFO, or HIFO methods, and shows you exactly which lots have losses and their holding periods—so you can harvest with confidence before year-end.

Disposal Methods: How You'll Match Lots to Sales

When you sell crypto, the IRS assumes you use first-in-first-out (FIFO)—the oldest lot first—unless you specify otherwise. You can instead use last-in-first-out (LIFO) or highest-cost-first (HIFO). Each method produces different gains and losses.

To use LIFO or HIFO, most experts recommend writing down the lot you're selling on the day of the sale—or in your tax software when you file—as "specific lot identification." Your broker may have a form or field for this. If you don't specify and you're using an exchange like Coinbase, they'll assume FIFO by default.

Before December 31, decide which method suits your situation. If you have large unrealized gains on old lots (FIFO would trigger huge gains) and newer cheap lots with losses, LIFO or HIFO can let you harvest those losses without selling your biggest gainers.

What Happens When Brokers Report

Brokers began reporting digital-asset sales on Form 1099-DA for transactions on or after January 1, 2025. The form shows the proceeds of your sale. For 2025 transactions (filed in early 2026), the IRS gave brokers penalty relief for good-faith reporting, and many brokers are still refining how they calculate and report cost basis. Don't assume your 1099-DA has your correct cost basis—especially if you moved coins between wallets, accounts, or exchanges. Your own records are the primary source.

Form 8949 is where you reconcile what the broker reported to you and the IRS against what you actually report on your return. If there's a mismatch, you explain it there. This is why keeping detailed lot records is critical—if an exchange reports proceeds of $5,000 but you think your cost basis was $2,000 when it was actually $3,000, Form 8949 is where you correct it.

Organize Your Records by December 31

To harvest losses confidently before year-end, finish your lot inventory by December 20 at the latest. This gives you ten days to execute sales and settle transactions before the close of the tax year. If you're holding on an exchange, you can typically sell and see the proceeds settle the same day or within one day. If you hold self-custody assets, settlement depends on blockchain confirmation times (usually minutes to hours) and your own process.

Steps to finalize:

1. Reconcile all exchange exports against each other; if you've transferred coins between platforms, match the date of transfer to verify the lot didn't get lost.
2. Calculate cost basis for each lot.
3. Identify all lots with unrealized losses (current value < cost).
4. Decide on a disposal method (FIFO, LIFO, or HIFO) and document it.
5. Rank losses by size and holding period to prioritize which to harvest.
6. Execute your sales by December 31 and keep the trade confirmations.
7. Export or save the final state of your cost basis and holdings as of December 31.

Deduction Limits on Capital Losses

If your capital losses exceed your capital gains, you can deduct the net loss against other income, but the amount is limited to the lesser of $3,000 ($1,500 if married filing separately) or your actual net loss. Any amount above the limit carries over to future years.

Example: You harvest $8,000 in losses and have $2,000 in gains. Net loss is $6,000. You can deduct $3,000 against other income (wages, interest, etc.) in the current year. The remaining $3,000 carries over to the next year.

This means if you're planning to harvest more than $3,000 in net losses, the excess won't reduce your taxable income until future years. That doesn't make harvesting a bad idea—it's still valuable tax planning—but it's important to understand the cap before you execute a large harvest.

FAQ

Can I sell a losing lot and buy the same cryptocurrency right back?

The tax treatment of repurchasing the same crypto after harvesting a loss is unsettled. The IRS has not issued definitive guidance on whether specific restrictions apply. Consult a tax professional about your situation before executing this strategy. Many filers currently repurchase after harvesting, but you should confirm the current rules before proceeding. If you do repurchase, keep detailed records showing the sale and repurchase as separate transactions on separate dates and at separate prices.

How much of my capital losses can I deduct?

The deductible amount is the lesser of $3,000 ($1,500 if married filing separately) or your net capital loss for the year. Any excess carries over to future years. To calculate it, sum all your capital gains and losses for the year (both crypto and other assets) and subtract losses from gains. If the result is negative, you can deduct up to $3,000 of the loss in the current year.

What if my broker didn't provide cost basis on my 1099-DA?

Many exchanges didn't report cost basis on initial 1099-DA filings in early 2026, or they reported it incorrectly if you moved coins between accounts. Your own records—exchange CSVs, deposit addresses, and transaction histories—are your proof. On Form 8949, you can report the proceeds from the 1099-DA and your own calculated cost basis, with an explanation of any difference. Keep copies of your exchange exports and any spreadsheets you used to calculate basis.

Do I need software to track lots and harvest correctly?

A detailed spreadsheet works for small portfolios. If you have dozens of trades across multiple exchanges, or if you trade frequently and want to model different disposal methods before deciding, dedicated software can be faster and less error-prone. The free tier at Hodl1099 covers up to 15 transactions per year; paid plans go up to 3,000 transactions. The key is having a single, auditable record of every lot, its cost, and its current status by the time you file or harvest.