Do you need to file a Self Assessment tax return in 2025/26?

The triggers, explained one by one

Most people land in Self Assessment because of a single line item — a side hustle, some dividends, a rental flat. Here is what each trigger actually means in practice (GOV.UK; LITRG):

Self-employed (sole trader) — gross income over £1,000

The £1,000 trading allowance is the line. Below it, no return needed. Above it — even if your net profit is small, even if you made a loss — you must register for Self Assessment and file. A consultant who invoiced £1,400 and spent £900 on costs still crosses the threshold. The test is on gross trading income, not profit.

Company directors — only with untaxed income

Being a director on its own is no longer a filing requirement. You file because you have untaxed income to declare — typically dividends above the £500 allowance, or benefits in kind that aren't handled via PAYE. A director who takes only a PAYE salary and no dividends may not need to file at all. The moment you take £501 of dividends, you do. See the dedicated Self Assessment for directors guide for how the dividend tax flows through your personal return.

Landlords — property income over £1,000

The £1,000 property allowance mirrors the trading allowance. Most landlords clear it easily on rent alone, so most landlords file. From 2026/27, landlords with qualifying property income over £50,000 move to Making Tax Digital for Income Tax and submit quarterly updates instead — but for the 2025/26 return (filed by 31 January 2027), the traditional Self Assessment rules still apply.

High earners — total income over £150,000

Total taxable income over £150,000 brings you into Self Assessment by itself, even if every penny was taxed correctly through PAYE. HMRC wants the return as a reconciliation. The threshold catches more senior employees each year as wages rise but the figure is held flat.

Capital Gains Tax — gains above £3,000

Gains above the £3,000 annual exempt amount need reporting. The CGT allowance has fallen sharply — it was £12,300 just two years ago — so far more disposals now produce a reportable gain. Note the separate 60-day CGT return for UK residential property (covered below) — that one runs on its own clock, independently of your annual Self Assessment.

High Income Child Benefit Charge

If you or your partner claim Child Benefit and either of you has income over £60,000, the High Income Child Benefit Charge applies. It tapers between £60,000 and £80,000 — above £80,000, the full Child Benefit is reclaimed. The higher earner is the one who must file Self Assessment to pay the charge, even if all other income is via PAYE. It catches a lot of dual-earner households who would otherwise never need to file.

Untaxed savings, investment or foreign income

Significant savings interest, dividend income from outside an ISA, or foreign income not collected via PAYE all push you into Self Assessment once the totals are material. HMRC handles small amounts of bank interest through your tax code; once it's substantial, the annual return is the mechanism for reporting it.

HMRC notice to file

If HMRC sends you a notice to file, you must file — even if no tax is due, even if none of the triggers above applies. The notice itself creates the obligation. The only way out is to ask HMRC to withdraw the notice in writing; until they do, the legal duty stands and the £100 automatic penalty applies if you miss the deadline.

The trap people miss: there's no exemption just because no tax is due

The most common misunderstanding is “I don't owe any tax, so I don't need to file.” That isn't how it works. If you meet a trigger — or HMRC has issued a notice — you must file the return, regardless of whether tax is due at the end of it. A side hustle that turned over £1,200 and produced a £100 loss still requires a return. Dividends of £600 with £11 of tax due still require a return. And a return demanded by HMRC under a notice must be filed even if every number on it is zero.

The penalty for missing the deadline doesn't care whether tax was owed either: the automatic £100 hits at one day late, even if you owed nothing or were due a refund. That's why the seasonal January panic catches so many people who “didn't think it applied to them.”

What counts as “untaxed income” for directors

For directors, the gateway phrase is “untaxed income.” In plain English, that means any income where the tax has not already been collected at source. The most common examples:

• Dividends above the £500 allowance — paid from company profit, never taxed via PAYE, always reported through Self Assessment.
• Benefits in kind that aren't payrolled — a company car, private medical, gym membership, beneficial loans — if not run through PAYE, they sit on your personal return.
• Director's loans outstanding at year end above £10,000, which can trigger a Section 455 charge on the company and a benefit on you.

The point: it's the untaxed income, not the role, that creates the filing obligation. See the directors and dividends spoke for the full mechanics of how a salary-plus-dividends split flows through your annual return — and the Salary vs Dividends guide for planning that split in the first place.

CGT and the separate 60-day reporting rule

One specific exception is worth flagging. If you sell a UK residential property and have a chargeable gain, you must file a separate 60-day CGT return and pay the tax within 60 days of completion — through HMRC's standalone CGT on UK Property service. That is in addition to declaring the same gain on your annual Self Assessment return as a reconciliation. The 60-day clock runs from completion of the sale, not from the end of the tax year, and it applies regardless of whether you would otherwise file Self Assessment.

Gains on non-property assets — shares, crypto, business assets — are reported only on the annual return. There is no separate 60-day rule for those.

Where to go next

• Self Assessment deadlines and key dates — the full 2025/26 timetable: 5 Oct 2026 to register, 31 Jan 2027 to file online.
• How to register and file — CWF1, SA1, SA401, getting your UTR, and the SA100 itself.
• Self Assessment penalties — how £100 grows into £1,600+ if a return is left unfiled.
• Self Assessment tax calculator — estimate your 2025/26 bill before you file.