# HMRC crypto penalties, nudge letters and CARF fines explained

Late Self Assessment triggers automatic penalties from £100. Inaccuracy penalties range from 0% to 100% of tax depending on behaviour. CARF can fine you up to £300 for not giving your NI number to a UK crypto provider. If you get an HMRC nudge letter about crypto, check your records and respond — do not ignore it.

## Key facts
- Late filing: £100 initial penalty, more after 3 and 6 months.
- Late payment: interest plus penalties after 30 days.
- Nudge letters are not fines — but ignoring them risks enquiry.
- CARF admin penalty: up to £300 for missing tax details.
- Voluntary disclosure usually reduces penalties.

## Late filing and payment penalties

Missing the 31 January Self Assessment deadline starts at £100, rising with further delays. Late payment accrues interest and penalties. Set a calendar reminder for 6 April (tax year end), 5 October (register), and 31 January (file and pay).
## Inaccuracy and failure to notify

Underpaying because of careless errors or failing to register for Self Assessment when required can lead to penalties of 0% to 30% of tax (careless) or higher if deliberate. Keeping good records supports a ‘reasonable care’ defence.
## HMRC nudge letters

HMRC sends letters when exchange data suggests undeclared gains. A nudge is an opportunity to review and correct — use the voluntary disclosure service if tax is owed. Ignoring letters can escalate to formal enquiry.
## CARF penalties from 2026

Failure to provide required personal and tax information to UK crypto service providers under CARF can result in an administrative penalty up to £300. Providers must collect data from 1 January 2026.
## What to do if you receive contact from HMRC

Do not panic. Gather records, compare against exchange statements, and seek professional help for large amounts. Respond within deadlines. If tax is owed, calculate interest and consider voluntary disclosure.

## FAQs
### Can HMRC see my DeFi wallet?

On-chain activity is not reported under CARF like exchange data, but you remain legally required to declare taxable events.

## Sources

- [HMRC — Self Assessment penalties](https://www.gov.uk/self-assessment-tax-returns/penalties)
- [HMRC — Tell HMRC about unpaid tax on cryptoassets](https://www.gov.uk/guidance/tell-hmrc-about-unpaid-tax-on-cryptoassets)
- [HMRC — Information for individuals (CARF)](https://www.gov.uk/guidance/information-you-need-to-give-to-uk-cryptoasset-service-providers)

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— Digital Assets UK (https://digital-assets.co.uk/tax/hmrc-penalties-and-nudge-letters/), reviewed 2026-06-23. Source: https://www.gov.uk/self-assessment-tax-returns/penalties