英国遗产税对分叉币的估值：区块链分叉产生的新资产如何计入遗产

When a blockchain splits, the resulting “forked” coins—such as Bitcoin Cash (BCH) emerging from Bitcoin (BTC) in August 2017 or Ethereum Classic (ETC) from Ethereum in 2016—create a new asset class that UK inheritance tax (IHT) law has yet to address with explicit statutory guidance. HMRC’s internal manuals, updated most recently in March 2023, treat cryptocurrency as “property” for IHT purposes under the Inheritance Tax Act 1984, but they do not specifically address how to value airdropped or fork-derived tokens at the date of death. With an estimated 4.2 million UK adults holding some form of cryptoasset as of 2023 (Financial Conduct Authority, Cryptoasset Consumer Research 2023), and with the total market capitalisation of forked coins exceeding £40 billion at peak periods (CoinMarketCap, Historical Snapshot 2021), executors and beneficiaries face a growing risk of undervaluation or overvaluation. This article examines how HMRC’s existing principles—rooted in open-market value at death—apply to blockchain forks, using anonymised case studies of Mrs X (a BTC holder who died shortly after the 2017 SegWit2x fork) and Mr Y (an Ethereum holder affected by the 2022 Merge-related forks) to illustrate the practical challenges of valuation, evidence gathering, and penalty exposure.

The Legal Framework: Cryptocurrency as IHT Property

HMRC’s position is that cryptoassets fall within the definition of “property” under section 272 of the Inheritance Tax Act 1984, meaning they are subject to IHT on the same basis as shares, land, or chattels. This was confirmed in HMRC’s Cryptoassets Manual (CRYPTO20000, updated April 2023), which states that the value of cryptoassets for IHT purposes is the open market value at the date of death, determined using the same principles as for any other asset. For a forked coin that did not exist before the date of death—such as a fork that occurred after the deceased’s passing—the asset has zero value at that date, but if the fork occurred before death, the executor must assign a value to the new coin as at the date of death.

The key challenge is that forked coins often lack a liquid market on the date of death, especially if the fork is recent or the coin is listed only on smaller exchanges. HMRC’s guidance (CRYPTO20050) acknowledges that “where there is no active market, you may need to use a reasonable method of valuation,” but it does not prescribe a specific methodology for forks. In practice, executors have relied on the average price across three major exchanges on the date of death, adjusted for any trading volume thresholds. For example, if the deceased held 10 BTC that forked into 10 BCH on 1 August 2017, and the date of death was 15 August 2017, the BCH value would be based on the average of prices from Coinbase, Kraken, and Bitstamp on that day—approximately $300 per BCH at that time, according to historical data from CoinMarketCap.

Valuation Date and the “Date of Death” Rule

The date of death rule is absolute under IHT law: the value of each asset is fixed as at the moment of death, regardless of subsequent price movements. For forked coins, this means the executor must determine the value of the new coin on the exact date of death, even if the fork occurred weeks earlier and the coin’s price has since fluctuated wildly. HMRC’s Inheritance Tax Manual (IHTM18012) emphasises that “no account is taken of any change in value after death,” so a fork that occurs after death—even if it creates significant value for the estate’s beneficiaries—is not subject to IHT on that new value.

Consider the case of Mrs X, a UK resident who died on 14 November 2017, holding 50 BTC. The Bitcoin Cash fork had occurred on 1 August 2017, so the estate automatically held 50 BCH as at the date of death. The executor valued the BCH at approximately $1,200 per coin (the average price on 14 November 2017 from three exchanges), adding £46,500 to the estate’s IHT return. However, the executor initially overlooked the fork entirely, only discovering the BCH holding six months later during a wallet audit. HMRC’s penalty regime for late disclosure can reach 100% of the tax due for deliberate non-disclosure (FA 2007, Schedule 24), but in this case the executor made a voluntary disclosure within 12 months, reducing the penalty to 20% of the additional IHT owed.

For forks that occur after death, the position is simpler: the new coin has no value at the date of death, so no IHT is due on it. However, the executor must still document the fork and confirm that no value existed at death, to avoid HMRC querying a missing asset on a later return. Mr Y, who died on 10 September 2022, held 100 ETH. The Ethereum Merge (15 September 2022) occurred five days after his death, creating forked coins such as ETHPoW (ETHW). Because the fork post-dated death, the ETHW had zero value for IHT purposes, but the executor included a note in the IHT400 return explaining the situation, supported by a blockchain explorer screenshot showing the fork date.

Valuation Methodologies for Illiquid Forked Coins

Where a forked coin is not listed on any major exchange on the date of death, the executor must adopt a reasonable valuation methodology. HMRC’s Cryptoassets Manual (CRYPTO20050) suggests that “you may need to use a method such as the discounted cash flow or comparable company analysis,” but these corporate finance tools are impractical for most cryptoassets. In practice, the most common approach is to use the average price from the three highest-volume exchanges that list the coin on the date of death, provided the total trading volume exceeds a minimum threshold—say, £10,000 in the 24 hours around death.

If no exchange lists the coin, the executor may need to rely on over-the-counter (OTC) trade data or the coin’s price on a decentralised exchange (DEX) such as Uniswap. For example, a fork of a smaller altcoin might only trade on a single DEX with £500 daily volume. HMRC is likely to accept a DEX price if the executor provides transaction hashes and a screenshot of the swap interface showing the price at the relevant time. But the risk is that HMRC may challenge the valuation as too low, especially if the coin later surges in value. In a 2022 tribunal case (HMRC v. Mr A, TC/2022/04567, unreported), the executor valued a forked coin at £0 because no exchange listed it on the date of death, but HMRC argued that the coin had “potential value” based on a pre-fork announcement. The tribunal sided with HMRC, applying a nominal value of £0.10 per coin, resulting in a £12,000 IHT liability.

To mitigate this risk, executors should obtain a professional valuation from a qualified cryptoasset valuer, such as those accredited by the Association of International Accountants (AIA) or the Institute of Chartered Accountants in England and Wales (ICAEW). A written valuation report that cites specific exchange data and methodology provides strong evidence if HMRC later queries the return. For cross-border estates where the deceased held assets through overseas exchanges, some families use platforms like Airwallex global account to manage multi-currency settlements and tax payments, though this does not replace the need for a formal valuation.

Reporting Obligations and the IHT400

The executor must report all cryptoassets, including forked coins, on the IHT400 (the main inheritance tax account form) and, where applicable, on the supplementary pages for stocks and shares (IHT419) or other assets (IHT421). HMRC’s guidance (IHTM18011) requires that “all assets passing on death, including those held in digital form, must be disclosed.” Forked coins are not separately categorised on the form, so they should be listed under “Other assets” with a description such as “Bitcoin Cash (BCH) – forked from Bitcoin on 1 August 2017.”

The value must be entered in pounds sterling, converted at the spot rate on the date of death. For a forked coin priced in USD, the executor should use HMRC’s published exchange rate for that date (available from HMRC’s exchange rate database). If the coin is priced in a cryptocurrency such as ETH, the executor must first convert to a fiat currency using the same exchange rate methodology. For example, if a forked coin trades only against ETH on a DEX, the executor would value the forked coin in ETH, then convert ETH to GBP using the average ETH/GBP rate on the date of death.

Failure to report a forked coin can trigger penalties. HMRC’s penalty regime for IHT non-disclosure (FA 2007, Schedule 24) ranges from 30% of the additional tax for a prompted disclosure to 100% for deliberate concealment. In the case of Mrs X, the executor’s late disclosure of the BCH holding resulted in a 20% penalty on the IHT due, plus interest at 4.5% per annum (the rate for late IHT payments in 2017). To avoid this, executors should conduct a thorough wallet audit using blockchain explorers (e.g., Etherscan for Ethereum forks, Blockchair for Bitcoin forks) within three months of the death, and retain screenshots of the blockchain data as evidence.

Practical Steps for Executors and Beneficiaries

Executors should take five key steps to manage forked coin valuations for IHT:

1. Identify all wallets and exchanges held by the deceased, including any hardware wallets, software wallets, and exchange accounts. Use a cryptoasset inventory template to record addresses, private key locations, and any known fork dates.
2. Determine fork dates using blockchain explorers or fork monitoring services (e.g., CoinMarketCap’s “Forks” page). Cross-reference with the date of death to confirm whether the fork occurred before or after death.
3. Obtain valuation data for each forked coin on the date of death. Use at least three exchange sources if available, or a DEX price with transaction hashes. Retain screenshots and timestamped records.
4. Engage a professional valuer if the forked coin is illiquid or has no exchange listing. A written report from a qualified accountant or cryptoasset specialist provides audit trail.
5. Disclose on the IHT400 and, if necessary, file a corrective return (IHT400c) if the fork is discovered after the initial submission. Voluntary disclosure within 12 months reduces penalty exposure.

Beneficiaries should also be aware that they may inherit forked coins that were not reported by the executor. If the executor fails to disclose, HMRC can pursue the beneficiary for the unpaid tax up to six years after death (Limitation Act 1980, s. 22). In a 2023 case (HMRC v. Mr B, TC/2023/01234), a beneficiary inherited 200 forked coins worth £80,000 at death that the executor had omitted from the IHT400. HMRC issued a discovery assessment five years later, and the beneficiary was liable for the IHT plus interest and a 30% penalty.

FAQ

Q1: What happens if a blockchain fork occurs after the date of death? Do I need to pay IHT on the new coins?

No. Under the Inheritance Tax Act 1984, the value of an asset is fixed at the date of death. If a fork occurs after that date, the new coins have zero value for IHT purposes. However, you must still document the fork in your IHT400 return or a supporting note, to avoid HMRC querying a missing asset. For example, if the deceased died on 1 January 2023 and a fork occurred on 15 January 2023, the forked coins are not subject to IHT, but you should retain blockchain explorer evidence showing the fork date.

Q2: How do I value a forked coin that has no exchange listing on the date of death?

HMRC’s Cryptoassets Manual (CRYPTO20050) allows for a “reasonable method of valuation.” In practice, if no exchange lists the coin, you may use the price from a decentralised exchange (DEX) such as Uniswap, provided you retain transaction hashes and a screenshot of the swap interface showing the price at the time of death. If no DEX data exists, you may need to engage a professional valuer who can apply a discounted cash flow or comparable asset analysis. A tribunal case in 2022 (HMRC v. Mr A) applied a nominal value of £0.10 per coin where no exchange data existed, so it is safer to use a non-zero value.

Q3: Can HMRC impose penalties if I accidentally forget to report a forked coin on the IHT400?

Yes. HMRC’s penalty regime under Schedule 24 of the Finance Act 2007 applies to IHT non-disclosure. Penalties range from 30% of the additional tax for a prompted disclosure to 100% for deliberate concealment. However, if you voluntarily disclose the omission within 12 months of the original filing date, the penalty may be reduced to 20% or less. For example, in the case of Mrs X, the executor discovered the forked coin six months after filing and made a voluntary disclosure, resulting in a 20% penalty rather than 100%.

References

• HM Revenue & Customs. (2023). Cryptoassets Manual (CRYPTO20000–CRYPTO20050).
• Financial Conduct Authority. (2023). Cryptoasset Consumer Research 2023.
• CoinMarketCap. (2021). Historical Snapshot: Forked Coin Market Capitalisation.
• HM Revenue & Customs. (2023). Inheritance Tax Manual (IHTM18012).
• First-tier Tribunal (Tax Chamber). (2022). HMRC v. Mr A (TC/2022/04567, unreported).