Tax-Loss Harvesting a Bitcoin ETF

TL;DR. Bitcoin ETFs in taxable accounts are good tax-loss harvesting candidates because bitcoin's drawdowns are deep and frequent enough to create harvestable losses regularly. The wash-sale rule of section 1091 disallows a loss if you rebuy "substantially identical" securities within 30 days. Whether a spot Bitcoin ETF falls inside that rule has never been settled by the IRS — there is no ruling or published guidance on point, and the funds' own filings do not claim there is. Practitioners handle the uncertainty by swapping issuers (IBIT → FBTC, IBIT → ARKB) rather than rebuying the same fund, and by matching the dollar amount rather than the share count.

Why bitcoin ETFs are good harvest candidates

Bitcoin is far more volatile than a broad equity index. A diversified S&P 500 holding can go years without a harvestable loss; a bitcoin position usually offers several a year. Measured on our own daily price series, three drawdowns landed inside eighteen months: −23.6% from 14 March to 8 July 2024, −20.5% in the eight days from 29 July to 6 August 2024, and −25.5% from 18 December 2024 to 11 March 2025.

So even a buy-and-hold investor who DCAs in regularly will hold lots with embedded losses at various points. Selling them to realise the loss, then immediately replacing the exposure with a similar but not identical fund, locks in the tax benefit without stepping out of the market.

The mechanics of tax-loss harvesting

1. Identify lots with embedded losses in your taxable account.
2. Sell those lots, realising the capital loss.
3. Within minutes, buy a different but functionally similar product to maintain market exposure.
4. The realised loss offsets capital gains elsewhere in your portfolio. If losses exceed gains, Publication 550 caps the deduction against other income at "$3,000 ($1,500 if you are married and file a separate return)".
5. Anything above that limit carries forward: "you can carry it over to later years until it is completely used up."

At a 20% long-term capital gains rate plus the 3.8% net investment income tax, a $10,000 harvested loss used against long-term gains is worth about $2,380. Used against ordinary income instead, the $3,000 annual cap is worth $720 a year to someone in the 24% bracket.

The wash-sale rule — and why its application here is unsettled

Publication 550 states the rule plainly: "A wash sale occurs when you sell or trade stock or securities at a loss and within 30 days before or after the sale you: Buy substantially identical stock or securities…" The loss is postponed, not destroyed — you "add the disallowed loss to the cost of the new stock or securities".

Whether a spot Bitcoin ETF sits inside that rule has never been settled, and sources that state it flatly are guessing. There is no IRS ruling or published guidance addressing spot bitcoin grantor trusts and section 1091, and the issuers do not claim there is: BlackRock's 10-K for the iShares Bitcoin Trust ETF for fiscal 2025, filed 27 February 2026, contains no occurrence of "wash sale", "substantially identical" or "section 1091" anywhere in the document. Its tax section stops short even of the trust's own classification — counsel's opinion is that the trust "should be classified as a 'grantor trust' for U.S. federal income tax purposes", "although not free from doubt due to the lack of directly governing authority".

And what Publication 550 says about "substantially identical" is a facts-and-circumstances test written for corporate stock: "you must consider all the facts and circumstances in your particular case. Ordinarily, stocks or securities of one corporation are not considered substantially identical to stocks or securities of another corporation." A grantor trust holding bitcoin is not a corporation, and the publication does not reach it.

The asymmetry settles the practical question: assume the rule applies. If it does and you ignored it, the loss is disallowed. If it does not and you complied anyway, you gave up only the option of instantly rebuying the identical fund. Direct bitcoin held outside a fund is a separate matter — it is property, not a security, and section 1091 does not reach it.

Swap fund pairings

Since the IRS has never ruled on whether two spot Bitcoin ETFs are substantially identical, most practitioners take the position that funds from different sponsors are distinct enough even when they track the same asset. That is a position, not a safe harbour. The pairings in common use: IBIT ↔ FBTC, the cleanest of them because Fidelity is the one issuer that custodies in-house rather than at Coinbase; IBIT ↔ ARKB, different sponsors with overlapping custody; FBTC ↔ HODL, no custodian in common; and IBIT ↔ Grayscale Bitcoin Mini Trust, different sponsors and very different fees, 0.25% against 0.15%.

Avoid rebuying the fund you just sold, and above all avoid rebuying it inside an IRA. Publication 550 names that case specifically — acquiring substantially identical stock "for your individual retirement arrangement (IRA) or Roth IRA" is a wash sale, and it is the one case excluded from the basis adjustment, so the loss is gone for good rather than postponed.

The numerical example

Scenario: a $50,000 IBIT position in a taxable account. Bitcoin falls and the position is now worth $40,000 — a $10,000 unrealised loss.

1. Sell the whole position, realising a $10,000 capital loss.
2. Immediately buy $40,000 of FBTC — the same dollar amount, not the same number of shares. Share prices differ from fund to fund, so matching share counts instead of dollars would change the size of your position, potentially by a large multiple.
3. Market exposure is unchanged; your tax position now carries a $10,000 realised loss.
4. At year end, offset it against $10,000 of capital gains elsewhere — about $2,380 saved at 20% plus the 3.8% NIIT.
5. With no gains to offset, deduct $3,000 against other income this year and carry $7,000 forward.

The bitcoin price can move between selling IBIT and buying FBTC. In practice the gap is seconds and the effect is small, but it is not zero.

What to track

• Cost basis per lot. Verify your broker is set to specific-lot identification rather than FIFO before the sale, not after.
• The 61-day window. 30 days before the sale and 30 days after it, plus the day of sale.
• IRA accounts. A repurchase inside your own IRA disallows the loss permanently.
• Spousal accounts. Publication 550: "If you sell stock and your spouse or a corporation you control buys substantially identical stock, you also have a wash sale."

Limits and caveats

• Harvesting is pointless inside a Roth or traditional IRA — nothing is realised there. It only works in taxable accounts.
• Carryforwards last until used up, but they are personal: unused capital loss carryovers do not pass to heirs.
• State conformity to the federal rules varies; check your own.

FAQ

Sources and further reading

• IRS Publication 550, "Investment Income and Expenses" — wash sales, substantially identical securities, and the capital loss deduction limit — irs.gov.
• iShares Bitcoin Trust ETF, Form 10-K for the year ended 31 December 2025, filed 27 February 2026 — sec.gov.
• Internal: Bitcoin ETF tax in the USA, Bitcoin ETF in a Roth IRA, IBIT vs FBTC.