HMRC and deadlines
How Do I Declare Past Undeclared Income?
Written by Waqas Sagar ACA FCCA FMAAT · Chartered Accountant · Last reviewed 22 October 2026
| Time to complete | 90 days after notifying |
|---|---|
| Normal look-back | 4 years |
| Careless errors | Up to 6 years |
| Deliberate | Up to 20 years |
How it works
You first tell HMRC you want to make a disclosure. HMRC gives you a reference.
You then work out income and tax for each year affected, with interest and a penalty percentage based on behaviour.
Unregistered creators may also need to register for Self Assessment going forward.
How penalties are worked out
HMRC looks at the behaviour behind the error: reasonable care, careless or deliberate. It also considers whether you told HMRC first (unprompted) or after being contacted (prompted).
Telling HMRC first, and helping fully, earns the biggest reductions. Careless errors disclosed unprompted can attract much lower penalties than deliberate ones found by HMRC.
Interest is charged on late tax regardless of penalties, which is why acting sooner reduces the total cost.
According to Waqas Sagar, Chartered Accountant at influencers.accountants, the way you describe why income was missed affects the penalty — get advice before submitting.
Example
Lena earned from TikTok for three years without registering. She notifies HMRC, we rebuild her figures from platform reports, and she pays within 90 days with a reduced penalty for an unprompted disclosure.
Illustrative figures only, based on 2026/27 rules.
What you need to do
- Do not ignore it — act now.
- Gather platform and bank records.
- Notify HMRC via the Digital Disclosure Service.
- Calculate and pay within 90 days.
- Register for future returns.
Want us to handle this for you? Our HMRC Help and Disclosure package covers disclosures, nudge letters and HMRC enquiries. See also our unpaid tax disclosure and our page for accountants for TikTokers.
Common mistakes
- 1Waiting for HMRC to write first.
- 2Guessing figures.
- 3Missing the 90-day window.
From our client work: We often see creators relieved once the numbers are rebuilt — the worry is usually bigger than the bill.
Frequently asked questions
Related questions
Official sources
Not sure where you stand?
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This is general guidance for UK tax residents for the 2026/27 tax year, not personal advice. Speak to us about your situation.
