HMRC 2026/27 Crypto Tax Deadlines: The Full Calendar

Missing a UK Self Assessment deadline is expensive and cumulative. For crypto in 2026/27, here are the dates that actually matter, in the order they hit — plus the penalty regime for each miss.

The tax year itself

The UK 2026/27 tax year runs from **6 April 2026** to **5 April 2027**. Every crypto disposal on or after 6 April 2026 up to and including 5 April 2027 belongs in this tax year. The date HMRC cares about is the disposal date, not when you get around to filing.

Only disposals that occur inside the tax year window count for 2026/27. If you sold ETH on 4 April 2027 that's still in the 2026/27 tax year; if you sold it on 6 April 2027 it's in 2027/28.

Deadline 1: register for Self Assessment — 5 October 2027

If you have never filed Self Assessment before and you have crypto to report (any disposals above the £3,000 allowance, or total proceeds over £50,000 even if under-allowance for 2026/27), you must register with HMRC by **5 October 2027**.

Register at gov.uk/register-for-self-assessment. It's free and takes about ten minutes. HMRC posts you a Unique Taxpayer Reference (UTR) and activation code by mail — the whole cycle can take 2-3 weeks, so don't leave this to January.

**Penalty for missing register-by:** £100 fixed, plus HMRC may assess "failure to notify" penalties of up to 100% of the tax owed if the register-by miss is what leads to eventual under-reporting.

Deadline 2: paper return — 31 October 2027

If you file on paper (rare in 2026), the deadline is **31 October 2027**. Almost no one does this for crypto because online filing gives you three more months. But if you're wedded to paper, this is your date.

**Penalty for missing paper deadline:** £100 fixed, then £10/day after 3 months, then 5% of tax owed at 6 and 12 months.

Deadline 3: online return + pay — 31 January 2028

The big one. Your 2026/27 Self Assessment online return must be filed, and any tax owed must be paid, by **31 January 2028**. Both — a filed-but-unpaid return still triggers late-payment penalties.

This is when HMRC receives your SA108 crypto figures: disposal count, proceeds, costs, gains, losses, AEA claimed, taxable gain, and the tax owed at your band. Also SA100 income boxes for any staking / airdrop / mining income at receipt.

**Penalty for missing 31 January:**

- **Day 1 late:** £100 fixed penalty, applied immediately. - **3 months late:** £10/day, up to 90 days = £900 additional. - **6 months late:** 5% of tax owed (minimum £300). - **12 months late:** another 5% of tax owed (minimum £300). - **Late payment:** interest at HMRC's rate (currently 7.5% on unpaid tax) accrues from 1 February.

Total downside for a £1,000 tax bill filed a year late: about £2,500 in penalties and interest on top. Do not miss this date.

Deadline 4: second payment on account — 31 July 2028

If your 2026/27 tax bill exceeded £1,000, HMRC requires two "payments on account" for 2027/28 — one on **31 January 2028** (with the 2026/27 balance) and one on **31 July 2028**. Each is 50% of your 2026/27 liability.

Payments on account can be reduced if you expect your 2027/28 income to be lower — form SA303 or online adjustment. But reducing them inaccurately triggers interest if the actual bill comes in higher.

Deadline 5: keep records until — 31 January 2034

You must keep the transaction-level detail supporting your 2026/27 SA108 for **six years** from the filing deadline — i.e. through **31 January 2034**. HMRC can open an enquiry within 12 months of filing (or 4 years if under-declared, or 20 years if the under-declaration was deliberate).

CryptoLens exports both the SA108-format PDF summary and a full disposal-level CSV. Save both; the CSV is the record that survives an enquiry, the PDF is the document that gets filed.

Special dates for CARF-affected users

The Crypto-Asset Reporting Framework (CARF) took effect **1 January 2026**. UK-serving exchanges report customer 2026 activity to HMRC by 31 May 2027 for the 2026 calendar year. Practically, this means HMRC has your Coinbase / Binance / Kraken / Revolut activity data before your 2026/27 return is due. Don't file numbers that materially disagree with the CARF submission.

If HMRC has already sent you a **nudge letter** — a soft prompt asking you to check your records — you typically have **60 days** to respond via the Digital Disclosure Service. See our <a href="/blog/hmrc-crypto-nudge-letter">nudge-letter guide</a> for the response playbook.

The calm-January playbook

Aiming to file in January is normal but stressful. A calmer flow:

- **October 2027:** register for SA if you haven't already. Import every exchange CSV + on-chain wallet into CryptoLens. Generate a first-draft SA108. - **November 2027:** classify anything ambiguous (staking, airdrops, DeFi income). Cross-check against Etherscan for any missing transactions. - **December 2027:** file the return. Set up payment for 31 January. - **January 2028:** relax. Actually enjoy the holidays.

If you're filing for prior tax years too — 2024/25, 2023/24 — factor an extra week per year of back-filing. CryptoLens handles multi-year automatically, but you'll want to sanity-check each year's summary independently.