AI agents for business finance: what they can and can't do
What AI agents can do in bookkeeping, close, collections and compliance today, where a person must stay in charge, and how to judge a product.
The short answer
A late UK Self Assessment return starts with a £100 penalty, then £10 a day after three months up to £900, then 5% of the tax due or £300, whichever is greater, at six months and again at 12 months. Late payment adds 5% of unpaid tax at 30 days, six months and 12 months, plus interest. Having Nigerian income does not change these amounts, but undeclared offshore income can bring higher penalties.
Returns with Nigerian income are often late for understandable reasons: waiting for a withholding tax receipt from a tenant, a Nigerian bank statement that will not download, or uncertainty about the exchange rate. HMRC's penalties do not distinguish. This guide sets out the charges as GOV.UK describes them and what to do now. It is information, not tax advice.
Late filing penalties
GOV.UK's Self Assessment penalties page (last public update November 2024) lists:
| How late | Penalty |
|---|---|
| One day | £100 |
| 3 months | £10 a day, up to a maximum of £900 |
| 6 months | A further 5% of the tax due or £300, whichever is greater |
| 12 months | Another 5% or £300, whichever is greater |
For the 2025 to 2026 tax year, the online deadline is 31 January 2027 and paper returns had to reach HMRC by 31 October 2026.
Late payment penalties
- 5% of the unpaid tax at 30 days late
- 5% of the unpaid tax at 6 months
- 5% of the unpaid tax at 12 months
- interest on the amount owed
GOV.UK says a penalty must be paid within 30 days of the date on the penalty notice. HMRC can change how these penalties are worked out, so check the GOV.UK page for the current position before relying on the figures.
Worked example
Example. Uche owes £2,000 of tax for 2024 to 2025, mostly on rent from a flat in Enugu. The online deadline was 31 January 2026. He files and pays on 31 October 2026, nine months late.
| Charge | Amount |
|---|---|
| Initial late filing penalty | £100 |
| Daily penalties, 90 days at £10 (capped) | £900 |
| 6-month penalty: greater of 5% of £2,000 (£100) or £300 | £300 |
| Late payment: 5% at 30 days | £100 |
| Late payment: 5% at 6 months | £100 |
| Total penalties before interest | £1,500 |
Interest is charged on top. Had he filed on time in January 2026 but paid late, only the late payment charges and interest would apply. Filing on time, even before you can pay, reduces the bill.
Penalties and interest are not deductible against your tax, and they cannot be credited against Nigerian tax. They are simply an added cost of filing late. If cash is the problem rather than paperwork, file on time and contact HMRC about paying in instalments; the late payment charges are smaller than the filing penalties in the example above, and they stop growing once the tax is paid.
Registration and failure to notify
If you never registered, GOV.UK says registering after 5 October and not paying all your tax by 31 January can bring a failure to notify penalty, based on the amount still unpaid. Our guide to registering with Nigerian income explains the dates.
When the Nigerian income was never declared
Penalties for inaccurate returns and failure to notify can be higher where the income is offshore. HMRC's Worldwide Disclosure Facility guidance refers taxpayers to separate HMRC factsheets on offshore penalties when they calculate what they owe. If earlier years of Nigerian income were never reported, read using HMRC's disclosure facility before you file anything. If HMRC has written to you already, see responding to an HMRC letter.
Why returns with Nigerian income run late
- Waiting for withholding receipts. File with the figures you have and the Nigerian tax you can evidence, then amend when receipts arrive.
- Exchange rate uncertainty. HMRC's notes say to convert at the rate when the income arose and link to HMRC's published rates; pick the rate, note it and move on.
- Two tax years. Nigeria runs January to December and the UK April to April, so a year's Nigerian rent has to be split by date.
- Agents who do not send statements. Ask for monthly or quarterly statements in writing, not only an annual total.
Appealing a penalty
GOV.UK says that if you have a reasonable excuse, you can appeal against a penalty. HMRC decides what counts; the GOV.UK appeal guidance gives examples. Waiting for Nigerian paperwork is unlikely to be enough by itself, because you can file using your best figures and amend later. Keep evidence of anything outside your control, such as a serious illness or a Nigerian office closure that stopped you getting essential records.
What to do now
- File as soon as you can, even with estimated Nigerian figures clearly noted, and amend when you have final ones.
- Pay what you can now to reduce late payment penalties and interest.
- Convert Nigerian amounts at the rate when they arose; see which exchange rate to use.
- Appeal any penalty within the time on the notice if you have a reasonable excuse.
Where Pryme fits
Late returns are often caused by missing paperwork. Statements from a Pryme account can be downloaded at any time, and a verifiable version through VerifyDoc.ai can be checked by an accountant as unaltered. See receipts and statements.
Questions people ask
What is the penalty for a late Self Assessment return?
£100 immediately, £10 a day after three months up to £900, then 5% of the tax or £300 at six and 12 months, whichever is greater.
Is there a penalty if I filed late but owe no tax?
The initial £100 late filing penalty is a fixed amount, not linked to the tax due. The percentage-based penalties use the greater of 5% of the tax due or £300.
Can I appeal a late filing penalty?
Yes, if you have a reasonable excuse. GOV.UK has appeal guidance; waiting for Nigerian documents is unlikely to be enough on its own.
Are penalties higher for undeclared foreign income?
Penalties for failure to notify and inaccuracies on offshore matters can be higher. HMRC's disclosure guidance points to separate offshore penalty factsheets.
Sources
- GOV.UK: Self Assessment tax returns, penalties (public update 5 Nov 2024) · accessed Oct 2026
- GOV.UK: Self Assessment tax returns, deadlines · accessed Oct 2026
- GOV.UK: Worldwide Disclosure Facility, make a disclosure (updated 6 Apr 2026) · accessed Oct 2026
This article is general information, not financial, legal or tax advice. Products described are provided under the terms on this site and are subject to regulation and eligibility.