Self assessment HMRC: top tips on how to finish your UK self assessment tax return online - and how to pay

• With the January 31 self assessment deadline days away, many organised taxpayers are feeling the pressure
• At this stage, HMRC prioritises timely submission and reasonable figures over perfection
• Focusing on the biggest income sources and reliefs can save time and stress
• Provisional figures are allowed and can be corrected later if needed
• There are options to manage the tax bill if the amount due comes as a shock

With just days to go until the self assessment deadline on Saturday, January 31, 2026, this is the point at which many otherwise organised people start to feel the pressure.

Not because they’ve ignored it all year, but because life, work and winter got in the way. But the good news is, at this stage, you don’t need to do everything. You just need to do the right things.

Here’s what genuinely needs your attention this week, and how to streamline the process without cutting corners or creating problems for yourself later.

What actually matters before January 31

At this point, HMRC cares about three things: that your return is submitted, your figures are reasonable and defensible, and any tax due is paid, or a plan is in place.

That’s it. Perfection is not the goal. Accuracy and timeliness are. If you’re still gathering paperwork, focus only on income and reliefs that materially affect your tax bill. Chasing a £12 bank interest certificate at 11pm is rarely worth the stress.

What to prioritise

This week, concentrate on the areas that most often trip people up, especially higher earners and those with multiple income streams:

• Employment income: Check your P60 and any P11D benefits match what HMRC already holds.
• Self-employed or freelance income: Use your actual figures where you have them, and sensible estimates where you don’t (HMRC allows this, as long as you amend later if needed).
• Dividends and interest: Don’t forget accounts outside ISAs, as even small amounts can push you over allowances.
• Property income: Rental income, allowable expenses and any changes to mortgage interest relief.
• Capital gains: Property sales, second homes, or investments sold during the year.

If something doesn’t apply to you, don’t overthink it. Blank boxes are fine.

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Use estimates strategically (but legally)

One of the biggest misconceptions is that every number must be exact by January 31. In reality, HMRC allows you to submit a return using provisional figures, provided you clearly mark them as estimates, and correct them later if needed.

This is often far better than missing the deadline entirely. A return can be amended after submission, but a late filing penalty is immediate.

Streamline your return

If you’re short on time, this approach works well:

1. Use last year’s return as a template: Most people’s financial lives don’t change dramatically year to year. Comparing with last year helps spot missing income or duplicated entries quickly.
2. Ignore optimisation for now: Advanced tax planning, pension carry-forward calculations and complex relief claims can wait. This week is about compliance, not cleverness.
3. Accept “good enough” admin: If your records are broadly accurate and supported by bank statements or invoices, that’s sufficient. HMRC is far more concerned with honesty than immaculate spreadsheets.

How to pay if you’re surprised by the amount you owe

If you owe tax and the amount makes you wince, you still have options:

Payments on account can sometimes be reduced if your income has fallen, and Time to Pay arrangements can be set up online for most people, spreading the cost without penalties.

Paying something is always better than paying nothing, and the worst option is avoiding the issue altogether.