You missed the 31 January deadline
You're already accruing the £100 fixed penalty plus daily penalties and interest. The fastest way to stop the meter is to file — even if you can't pay in full straight away.
Late & amended crypto returns
Late, amended, or undeclared crypto tax — fixed properly.
Missed the 31 January deadline, need to amend a return, or have crypto activity you haven't yet declared? We prepare the figures to HMRC standards and help you file the right way.
Late Self Assessment filings
Amendments within 12 months
Voluntary disclosures (DDS)
Penalties and interest accrue every day past the deadline. Coming forward voluntarily — before HMRC contacts you — typically attracts the lowest penalty bands.
Which situation is yours?
All of these are fixable — the route just depends on the facts
The right approach depends on how late you are, what's already been filed, and whether HMRC has contacted you. We'll confirm the right path on the call before any work begins.
You filed but didn't include crypto
You can amend a Self Assessment return within 12 months of the filing deadline. Beyond that window you'll need a voluntary disclosure (DDS) instead.
You included crypto but the figures were wrong
Common: using exchange CSVs without on-chain reconciliation, missing same-day/30-day matching, or treating staking and DeFi rewards as gains rather than income.
You have several years to catch up on
Multi-year disclosures are standard. We work backwards from your most recent year and price the whole scope as a single fixed fee.
How we help
Stop the penalty clock, then put the position right
Step 1
Scope the catch-up
Short call to confirm which tax years are in scope, what HMRC already knows, and whether this is an amendment, a late filing, or a voluntary disclosure.
Step 2
Reconcile and calculate
We pull exchange and on-chain history together, apply HMRC's pooling and matching rules, and separate income from capital gains correctly.
Step 3
File or disclose
Numbers and supporting workings go into the right route — return amendment, late filing, or DDS submission — with clear documentation if HMRC follows up.
Who you'll be working with
UK-qualified, crypto-specialist, accountable.
BlockBooks is led by Tim Whitehouse, EY-trained and a former cloud accounting firm founder. Late filings and disclosures are handled directly — you won't be passed around a call centre.
UK Self Assessment specialistFull audit trail of workingsFixed fee before work begins
FAQ
Common questions when you're behind
What are the penalties for filing late?
£100 fixed penalty as soon as you miss the 31 January deadline. After 3 months HMRC adds daily penalties of £10 per day (capped at £900). After 6 and 12 months further penalties apply, alongside interest on any tax owed. Filing as soon as possible stops further penalties accruing.
How long do I have to amend a return?
You can amend a Self Assessment return online within 12 months of the original 31 January deadline. After that window, a correction has to go through HMRC's voluntary disclosure process instead.
How far back can I go?
For careless errors HMRC can typically assess back 6 years, and up to 20 years for deliberate behaviour. A voluntary disclosure usually requires you to bring all in-scope years up to date, not just the most recent.
Will I be penalised more for coming forward?
Generally the opposite. Unprompted voluntary disclosures attract significantly lower penalty bands than corrections forced by an HMRC enquiry. The earlier you act, the better the outcome.
What does this cost?
Straightforward single-year cases start around £250. Multi-year catch-ups are quoted as a single fixed fee once we've scoped the wallets, exchanges and complexity. You'll see the number before any detailed work starts.