How Can I Prove the Value of Crypto for My Accounts

Why proving crypto value matters

HMRC treats cryptocurrency as a chargeable asset rather than currency, which means you must calculate gains, losses, and income in pounds sterling. Whether you are an individual reporting Capital Gains Tax or a company preparing accounts for Corporation Tax, the values you use must be supported by reliable evidence.

Without accurate records, you may face questions from HMRC or difficulty reconciling your figures later. Clear valuation evidence also helps you:

• Calculate Capital Gains or Income Tax correctly

• Prepare financial statements accurately

• Support your accountant during audits or reviews

• Defend your position in case of an HMRC enquiry

What HMRC expects

HMRC expects taxpayers to maintain detailed records of all crypto transactions. Each entry should show the sterling value at the time of the transaction, not at the end of the year.

You must record:

• The date of each acquisition or disposal

• The type and amount of cryptocurrency involved

• The pound sterling value at the time of each transaction

• Transaction fees paid

• Wallet addresses and exchange details

Records must be kept for at least five years after the Self Assessment deadline, or six years for companies filing Corporation Tax.

Using exchange data to determine value

The most reliable way to prove the value of cryptocurrency is to use the market data from the exchange where the transaction took place.

If you bought or sold crypto on a recognised exchange such as Binance, Coinbase, or Kraken, you can use the trade confirmation or transaction history as evidence. Most exchanges show the value of each transaction in both crypto and fiat currency.

If your exchange does not provide a sterling value, you should convert it using a reputable price index or data aggregator such as CoinMarketCap or CoinGecko. Use the market rate at the exact date and time of the transaction.

Example:
If you sold 0.5 Bitcoin at 2 pm on 5 May 2025, find the market rate for Bitcoin in pounds sterling at that time. Multiply it by 0.5 to calculate the value in pounds. Keep a screenshot or PDF of the data source for your records.

How to convert crypto to pounds sterling

When the exchange or wallet reports values in another currency (for example, US dollars), you must convert the amount to pounds sterling using the official exchange rate on the transaction date.

HMRC recommends using:

• The Bank of England exchange rate for that day, or

• The rate published by a recognised financial source

Consistency is important. Use the same data source for all conversions throughout the tax year and record which source you used in your notes.

Valuing crypto received as income

If you receive cryptocurrency as income, such as through mining, staking, airdrops, or payment for services, you must record the sterling value on the date you received it.

The easiest way to prove this is to take a timestamped valuation from the exchange or blockchain explorer showing the market value at the time of receipt.

Example:
You receive 0.2 Ethereum on 10 August 2025 at 11:30 am. You check its value on your exchange at that time and find it equals £500. Record £500 as your taxable income and retain a screenshot of the data.

Valuing crypto held in a business

If a limited company holds cryptocurrency, it must show the asset’s value in the balance sheet. The valuation is usually based on the cost of acquisition.

At the company’s year end, the accountant must review the market value to determine whether an impairment adjustment is needed if the crypto’s value has fallen below cost.

To support this, companies should keep:

• Trade confirmations and invoices showing purchase cost

• Year-end valuations using reliable market data

• Supporting evidence such as exchange rate screenshots or transaction reports

An accountant can advise whether crypto should be classed as a current or intangible asset depending on its purpose.

Handling multiple exchanges and wallets

Many crypto users hold assets across several exchanges and wallets. This makes proving value more complex, but the same principles apply.

You should:

• Maintain transaction histories from each exchange or wallet

• Record values in a single spreadsheet showing dates, types of crypto, quantities, and sterling values

• Keep records of transfers between wallets to show they are internal movements rather than taxable disposals

Using crypto portfolio software such as Koinly, CoinTracker, or Accointing can automate much of this process. These tools link to your wallets and exchanges, convert transactions to sterling, and generate detailed reports suitable for HMRC or your accountant.

Using blockchain data as evidence

If your transactions occur on a decentralised exchange (DEX) or directly on the blockchain, you can still prove the value using:

• The transaction hash from the blockchain explorer

• The wallet addresses involved

• A market price reference from the same date and time

For example, if you swapped tokens on Uniswap, record the transaction hash and check a crypto price index to find the market rate in sterling at that time.

You can then show that value as the disposal amount for your tax records.

What happens if records are incomplete

If you cannot provide evidence for the value of your crypto transactions, HMRC may estimate your gains based on available market data. This could result in an inaccurate tax calculation or an investigation.

To avoid this, always:

• Keep screenshots of transaction confirmations

• Export CSV or PDF reports from exchanges at least once a year

• Back up records securely offline or on cloud storage

Even small or experimental crypto transactions should be documented because they can add up over time and create a tax liability.

Proving historical crypto values

If you need to value crypto purchased several years ago and cannot access historical records from your exchange, you can use reputable crypto price archives.

Websites such as CoinMarketCap and Investing.com maintain historical price data for most coins. Take the price for the relevant date and time and use it to calculate your cost basis.

Document the source clearly in your records so HMRC can see how you arrived at the figure.

Final thoughts

To prove the value of cryptocurrency for your accounts, you must keep clear and consistent evidence showing how each transaction was valued in pounds sterling. Use exchange data wherever possible, and if that is unavailable, use a recognised price index or market rate from a reputable source.

HMRC expects complete and accurate records, so saving trade confirmations, wallet information, and exchange rates is essential. Whether you are an individual investor or a business, maintaining these records not only ensures compliance but also protects you in the event of an audit or enquiry.

With proper documentation and a consistent valuation method, you can manage your crypto accounts confidently and meet all HMRC requirements.