SATR CoachSelf Assessment, decoded

Self Assessment, decoded.

Plain-English help with your UK Self Assessment tax return — the latest HMRC updates, what to do, what to avoid, and when. Free, no sign-up.

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Every update linked to GOV.UK

Dated, not vague

Plain English, no jargon

Latest from HMRC

Plain-English summaries of official GOV.UK and HMRC updates for Self Assessment filers — each linked to its source.

New to MTD? Quarterly updates start this year → read the MTD guide

Updates begin soon — meanwhile, start with GOV.UK's Self Assessment guidance.

Who are you?

Plain-English guidance for three common Self Assessment situations.

Self-employed

You run your own business and pay tax on profits through Self Assessment — not via PAYE on a salary.

Do's

  • Keep records of all income and allowable expenses throughout the year.
  • Set aside money for tax and National Insurance as you earn.
  • Register for Self Assessment by 5 October if you are newly self-employed.

Don'ts

  • Do not mix personal and business spending without clear records.
  • Do not miss the 31 January filing and payment deadline.
  • Do not claim expenses you cannot explain or evidence if HMRC asks.

Read the full guide →

Sole trader

You trade in your own name. Your business income and personal tax affairs are reported together on one Self Assessment return.

Do's

  • Use separate bank accounts where possible to simplify bookkeeping.
  • Claim only expenses wholly and exclusively for the business.
  • Check whether you need to register for VAT as turnover grows.

Don'ts

  • Do not assume all home costs are deductible — use the rules correctly.
  • Do not forget Class 2 and Class 4 National Insurance on profits.
  • Do not file late because you are waiting for every last receipt.

Read the full guide →

Ltd company director

Your company is a separate legal entity. You may need a personal Self Assessment return for dividends, benefits, or other untaxed income.

Do's

  • Understand what salary and dividends you have taken in the tax year.
  • File your company accounts and Corporation Tax return on time.
  • Complete a personal return if HMRC asks or your circumstances require it.

Don'ts

  • Do not treat company money as your own without proper records.
  • Do not ignore a notice to file a Self Assessment return.
  • Do not assume the company return covers your personal tax position.

Read the full guide →

Tips & tricks

Practical reminders to keep your return on track.

Start with your UTR

Your Unique Taxpayer Reference is on HMRC letters and your online account. You need it to file.

Use your Government Gateway

Sign in at GOV.UK to file online, view payments, and check what HMRC thinks you owe.

Allow time for payments

Bank transfers can take a few days. Pay before 31 January to avoid late-payment interest.

Keep digital copies

Photos and scans of receipts are fine if they are readable and you can find them later.

Payments on account

If you owe enough tax, HMRC will ask for advance payments in January and July. Budget for both.

Check your tax code

If you also have PAYE income, an incorrect code can mean you underpay or overpay during the year.

Want the detail? Browse the guides →

Key dates

The next Self Assessment deadlines.

in 19 days

Second payment on account

MTD

MTD quarterly update (6 April – 5 July)

Register for Self Assessment if you are new or not yet registered

Paper filing deadline

Online filing deadline, balancing payment, and first payment on account

Second payment on account

Add these dates to your calendar

Full deadline and penalty detail in the Self Assessment deadlines guide →

SATR Coach is independent guidance, not tax, legal or financial advice, and is not affiliated with HMRC or GOV.UK. Always check GOV.UK or speak to a qualified accountant or tax adviser for your own circumstances.