Most people asking this question have read three articles that contradict each other. Two of the rules changed recently and a lot of published guidance never caught up.
Here is the current position, then twelve concrete situations with a straight answer for each.
The five situations where filing is mandatory
You must send a Self Assessment tax return if, in the last tax year, any of these applied:
| Trigger | Detail |
|---|---|
| Self-employed as a sole trader | Earned more than £1,000 gross, before deducting any expenses |
| Partner in a business partnership | No income threshold — being a partner is enough |
| Had Capital Gains Tax to pay | On selling or disposing of something that increased in value |
| Had to pay the High Income Child Benefit Charge | And you do not pay it through PAYE |
| Off-payroll worker repaying a student or postgraduate loan | Applies where you work through an intermediary under IR35 |
Beyond those five, you may also need to file if you have untaxed income — rental income, tips and commission, savings interest, dividends, foreign income, or taxable UK income while non-resident.
Two things most articles get wrong
The trading threshold is still £1,000. A rise to £3,000 has been announced but has no legislated commencement date, and the government has committed only to introducing it within this parliament. Articles telling you that you can earn £3,000 from a side hustle without filing are describing a future that has not arrived. When it does, it removes the return requirement — not the tax.
The £100,000 and £150,000 income triggers are gone. Earning over £100,000 through PAYE used to pull you into Self Assessment automatically. That applied up to 2022/23; £150,000 applied for 2023/24 only; both were removed from 2024/25. There is now no income-level filing trigger for PAYE-only taxpayers.
The twelve scenarios
1. The side hustle seller
You sold £2,400 of secondhand clothes and refurbished furniture on an online marketplace last year.
It depends what you were doing. Selling your own possessions is not trading, whatever you raise — though a single item sold for a large gain can trigger Capital Gains Tax. Buying to resell is trading, and once gross receipts pass £1,000 you must register and file. The allowance is measured before expenses, so £1,400 of turnover with £900 of costs still crosses the line.
2. The landlord
You rent out one flat and receive £11,000 a year.
Yes. Property income is untaxed income and needs a return. A separate £1,000 property allowance means very small amounts fall outside it — £11,000 clearly does not. And if your combined qualifying income from self-employment and property is over £50,000, you are already inside Making Tax Digital for Income Tax and filing quarterly.
3. The limited company director
You are the sole director of your own company and take a small salary plus dividends.
Not automatically. Being a director is not itself a filing trigger — the single most misreported point in UK tax content. You will usually still file, but because of what you receive, not what you are: dividends above your allowances, benefits in kind, or a director’s loan. Take nothing but a salary within the personal allowance, with no other income, and there may be no requirement at all.
4. The high earner on PAYE
You earn £140,000 as an employee. No property, no side income, no investments outside an ISA.
No. There is no income-level trigger any more. HMRC collects the tax through your code, including the personal allowance taper that starts at £100,000. If HMRC has issued you a notice to file, you must still file or ask to be taken out of Self Assessment — the notice creates the obligation.
5. Capital gains on a second property
You sold a buy-to-let in September and made a £70,000 gain.
Yes, twice. UK residential property has its own reporting route: report and pay the Capital Gains Tax within 60 days of completion, then report the disposal again on your Self Assessment return for that tax year. Missing the 60-day window is a common and expensive error.
6. The crypto investor
You disposed of cryptoassets during the year — sold for cash, swapped one token for another, or spent them.
Probably yes. HMRC treats cryptoassets as chargeable assets for most individuals, and a swap counts as a disposal, not just a cash-out. If total taxable gains exceed the annual exempt amount — £3,000 for 2026/27 — you have Capital Gains Tax to pay, which is a mandatory trigger. Where activity is frequent and organised enough to amount to trading, it is income rather than capital.
7. Foreign income
You have a rental property in Spain, or dividends from a US brokerage account.
Yes, if you are UK resident and taxed on the arising basis. HMRC lists foreign income as a reason to file. Tax paid abroad does not remove the reporting requirement — you claim relief for it on the return.
8. The High Income Child Benefit Charge
Your adjusted net income is £68,000 and your household receives Child Benefit.
Only if you have not opted for PAYE. The threshold is £60,000 of adjusted net income, with full clawback at £80,000 — you repay 1% of the Child Benefit for every £200 over £60,000, and the higher earner pays it. Since summer 2025 the charge can be collected through your PAYE tax code, and if you do that, HICBC alone does not force you into Self Assessment. Use Self Assessment if you must file for another reason, or if it is past the following 31 January.
9. The off-payroll worker with a student loan
You work through your own company on an inside-IR35 engagement and are repaying a student loan.
Yes. One of the five mandatory triggers in its own right — it exists because student loan repayments are not always correctly collected through the deemed employment payment.
10. The partner
You joined a two-person consulting partnership in June and drew £14,000.
Yes. Being a partner is a trigger with no threshold. The partnership files its own return; you file a personal one showing your share. If the partnership return is late, every partner gets a penalty — not just whoever was meant to file it.
11. The first-year sole trader
You started freelancing in November 2025 and invoiced £6,200 by 5 April 2026.
Yes. You crossed £1,000 in 2025/26, so you must register by 5 October 2026 and file by 31 January 2027. Use form CWF1 rather than SA1 — CWF1 enrols you for Class 2 National Insurance as well as Self Assessment. If you were already registered for another reason, you still need to submit CWF1 when you start trading, or you will have a gap in your NI record.
12. Filed before, but not any more
You closed your business two years ago but HMRC still sends you a return each January.
You must tell HMRC. The obligation does not lapse on its own — while a notice to file is outstanding, a return is legally due and a £100 penalty applies if it is not sent. Use HMRC’s online form to close your record or be removed for a specific year, well before 31 January so HMRC has time to review it.
Frequently asked questions
Do I need to file a tax return if I earn under £1,000 from self-employment?
No. The trading allowance means gross self-employed income of £1,000 or less does not require a return. The £1,000 is measured before expenses, so check your turnover rather than your profit.
Has the self-employment threshold gone up to £3,000?
Not yet. The increase has been announced but has no legislated commencement date, and the government has committed only to introducing it within this parliament. Until it takes effect, the threshold is £1,000.
Do company directors have to file a Self Assessment tax return?
Not simply because they are directors. Directors usually file because of dividends above their allowances, benefits in kind or a director’s loan — but where none of those apply, there may be no requirement.
Do I have to file if I earn over £100,000 through PAYE?
No. The £100,000 trigger applied up to 2022/23 and the £150,000 trigger to 2023/24 only. Both were removed from 2024/25, and there is now no income-level filing trigger for PAYE-only taxpayers.
What happens if HMRC sends me a notice to file but I do not need to?
The notice creates a legal obligation, so you must either file or formally ask HMRC to withdraw it. Ignoring it results in a £100 penalty even if no tax is due.
Not sure which side of the line you are on
The genuinely difficult cases are above — trading versus selling possessions, a director with mixed income, a part-year of trading. Worth getting right first time, because registering late costs money even when the tax bill is small.
SmartFiling files Self Assessment returns for a fixed fee, including MTD for Income Tax where it applies. Three-week turnaround from receiving your records, and every return is reviewed and signed off by an ICAEW Chartered Accountant.
