Self Assessment & HMRC guides

14 guides

Tax returns, deadlines, penalties and paying HMRC — plus what the letters mean and how to put a mistake right.

HMRC Tax Refund: How to Check, Claim and How Long It Takes

HMRC refunds some overpaid PAYE tax automatically, but not the kind caused by unclaimed expenses, pension relief or a mid-year job change. Here is how to check what you are owed, claim it free, and how long the money takes.

By Maria Moisei · 24 Sept 2026

P800 Letter Explained: Refund, Underpayment and What to Check

A P800 is HMRC's end-of-year PAYE tax calculation, telling you whether you overpaid or underpaid. Here's how to claim a refund for free, what happens if you owe, and how to check the figures against your P60.

By Damon Smith · 24 Sept 2026

How to Pay Your Self Assessment Bill: Every Method and Deadline

Every way to pay your Self Assessment bill, how long each method takes to clear, the reference number HMRC needs, and what to do if you can't pay in full by 31 January.

By Mercy Oyelowo · 24 Sept 2026

HMRC Says I've Underpaid Tax: Why It Happens and What to Do

A letter saying you owe tax is usually a PAYE mismatch, not a mistake you made. Here's how to check the figures, when HMRC can write the arrears off under ESC A19, and how to pay or spread the bill.

By Damon Smith · 24 Sept 2026

How to Fill In a Self Assessment Tax Return: Step by Step for 2025/26

A plain-English walkthrough of the online Self Assessment tax return for 2025/26 — what to gather first, how to tailor each section, and the mistakes that cost people money.

By Mercy Oyelowo · 24 Sept 2026

Do I Need to File a Tax Return? The Self Assessment Rules for 2026

A plain-English checklist of who must file a Self Assessment return for 2026/27 — including the £1,000 side income test, the Child Benefit charge, and why a £150,000 salary is no longer a trigger on its own.

By Mercy Oyelowo · 24 Sept 2026

HMRC Personal Tax Account: What You Can Check, Claim and Fix

The HMRC personal tax account is where you check your tax code, pay records, National Insurance and State Pension forecast — and where most refunds and reliefs are claimed. Here's what you can actually do in it.

By Laura Michelle Davis · 24 Sept 2026

How Far Back Can HMRC Go? The 4, 6 and 20-Year Rules

HMRC can normally reassess four years of tax, stretching to six years for careless mistakes and 20 years for deliberate ones. Here is how each time limit works, and why your own refund window is only four years.

By Laura Michelle Davis · 24 Sept 2026

HMRC Scam Texts, Calls and Emails: How to Spot a Fake

HMRC never texts or emails you a link to claim a tax refund, and never demands payment in vouchers or crypto. Here is how to spot an HMRC scam, check a P800 refund is genuine, and report it.

By Laura Michelle Davis · 24 Sept 2026

Self Assessment Penalties: What You Owe at 1 Day, 3 Months, 6 Months and a Year

Miss the 31 January deadline and you owe £100 on day one. Miss it by a year on a £9,000 bill and penalties hit £3,250, because late filing and late payment are two separate ladders running at once.

By Mercy Oyelowo · 6 Sept 2026

Simple Assessment Explained: The PA302 Letter and What to Do When the Figures Are Wrong

A Simple Assessment is HMRC telling you what it thinks you owe, not a return you file. You get 60 days to challenge the figures, and savings interest is where they most often go wrong.

By Maria Moisei · 6 Sept 2026

Self Assessment: register by 5 October or face a penalty

If you need to file a Self Assessment return for the first time, you must tell HMRC by 5 October following the end of the tax year. Registration is not instant — a UTR arrives by post and can take ten working days or more, so leaving it late risks missing the January filing deadline too.

By Mercy Oyelowo · 21 Aug 2026

Payments on account: why your January tax bill is 150% of what you expected

If your Self Assessment bill is over £1,000, HMRC also asks for two payments on account towards next year, each half the current year's liability. That makes the first January demand 150% of the tax actually owed for the year just ended.

By Mercy Oyelowo · 21 Aug 2026

Self Assessment Tax Returns 2026: Deadlines, Penalties and How to File

Understand self assessment tax return deadlines, who needs to file, the penalties for missing them, and the simple steps to file your return with HMRC.

By Mercy Oyelowo · 17 Jun 2026

Deadlines, rate changes and what to claim

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Self Assessment & HMRC guides

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Deadlines, rate changes and what to claim