Audit-ready crypto records: what to keep, and for how long

Transaction evidence, price sources, wallet ownership proof and policy memos, plus the IRS, HMRC and SARS retention periods that apply.

2026-10-17 · 6 min read

If an auditor or tax authority asks how you got a number, the answer has to come from records you kept at the time, not from a block explorer you search later. Tax authorities expect you, not your exchange, to hold that evidence, and the retention clock often runs much longer for crypto than people assume.

Why exchanges and explorers are not your records

HMRC says plainly that exchanges may keep transaction records only for a short time, or may no longer exist by the time a return is prepared, so the duty to keep records sits with the taxpayer [4]. The same logic applies to any third-party data feed: a provider can change its methodology, relabel a transaction or shut down. Export and store your own copies at each period end.

What the authorities say to keep

The IRS asks taxpayers with digital assets to keep records of each purchase, receipt, sale, exchange or other disposition, and of the US dollar fair market value of digital assets received as income or as payment [2]. HMRC lists, for each transaction, the type of token, the date, whether it was bought or sold, the number of units, the sterling value at the date of the transaction, the running total of units held, and bank statements and wallet addresses in case of an enquiry [4].

For companies, UK law adds general accounting records: money in and out, assets and debts, and supporting documents such as invoices and bank statements [5]. Failing to keep proper records can lead to a 3,000 pound fine from HMRC or disqualification as a director [5].

A practical evidence pack

In practice, an audit-ready file for a crypto entity tends to have five layers. None of these is a formal checklist from a standard setter; they map the requirements above to what reviewers typically ask for.

• Transaction evidence: transaction hashes, chain, block time, wallet, counterparty, asset, quantity and fee for every on-chain movement; exchange statements, fill reports and deposit or withdrawal confirmations for custodial activity.
• Price evidence: for every valued event, the source used, the timestamp requested, the timestamp the price actually relates to, and the value. HMRC and the IRS both tie value to the date of the transaction [2][4], so a day-close price used for an intraday trade should be documented and justified.
• Wallet ownership: a register of every address the entity controls, who controls it, when it was added, and evidence of control (for example a signed message or a small test transfer). Without this, transfers between your own wallets can look like disposals to third parties.
• Lot and basis records: how cost basis was assigned to each disposal, and the method used. In the US this now has a specific documentary angle (below).
• Policy memos: written, dated decisions on treatment that the standards leave to judgment, such as gas fees, staking rewards, wrapped tokens, bridges and spam tokens, approved before the period they apply to.

The US wallet-by-wallet records point

From January 1, 2025, US basis rules work wallet by wallet. Revenue Procedure 2024-28 gave a one-time safe harbor to allocate unused basis to the units held in each wallet or account as of that date [3]. A taxpayer using a global allocation rule had to describe it in its books and records before January 1, 2025, and complete the allocation by the earlier of its first disposal of that asset in 2025 or the due date of its 2025 return [3]. Going forward, specific identification of units in a self-custodied wallet must be made on the taxpayer's books and records no later than the time of the sale or transfer [3]. In other words, the record has to exist at the moment of the trade, not be reconstructed at year end.

How long to keep it

The property rule in the US matters most for crypto. Records supporting the basis of a token must be kept until the limitation period expires for the year you dispose of it [1]. A token bought in 2017 and sold in 2026 needs its 2017 purchase evidence for at least three years after the 2026 return is filed. The same logic underlies HMRC's note that records for long-lived assets must be kept longer [5].

SARS requires records in their original form, kept orderly and safely and open to inspection, and electronic storage is allowed as the Commissioner prescribes [6]. Keeping electronic records outside South Africa, or in a non-standard form, needs SARS authorisation [6][7]. Entities with a South African footprint and cloud-hosted ledgers should check this point.

These are tax rules. Auditors, lenders, investors and other regulators may require longer retention, and the IRS itself reminds taxpayers to check non-tax requirements before discarding anything [1]. Many finance teams simply keep crypto source data for the life of the entity, because the cost of storage is trivial next to the cost of rebuilding history.

What to do

• Export exchange statements, fills and wallet histories at every month end and store them in a system you control.
• Record the price source and timestamp alongside every valued event, not just the value.
• Maintain a dated wallet register with evidence of control for each address.
• For US taxpayers, confirm your Rev. Proc. 2024-28 allocation is documented and that specific identifications are recorded at the time of each disposal.
• Write and date policy memos before the periods they cover, and keep superseded versions.
• Set retention by the longest applicable rule, and keep acquisition records until the period for the disposal year has closed.

Sources

1. How long should I keep records? (IRS)
2. Digital assets (IRS)
3. Revenue Procedure 2024-28 (IRS)
4. CRYPTO10400 - Introduction to cryptoassets: record keeping (HMRC)
5. Running a limited company: company and accounting records (GOV.UK)
6. Record keeping (South African Revenue Service)
7. GEN-GEN-23-POL02 - Manage taxpayer record retention authorisation - External Policy (South African Revenue Service)

General information for finance teams, current as of publication. Not legal, tax or accounting advice.

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