Self Assessment guides
Every HMRC task,explained plainly.
One guide per job: finding your UTR, registering, paying HMRC, payments on account, penalties, expenses and more. Checked against GOV.UK for the 2025/26 tax year.
UTR numbers
UTR numbers
Find it, get one, and know what it's for.
- How to find your UTR numberLost your UTR? Your 10-digit Unique Taxpayer Reference is in your HMRC app, Personal Tax Account and old HMRC letters. Here's exactly where to look.3 min read · 2025/26
- How to get a UTR numberNeed a UTR? You get one by registering for Self Assessment with HMRC. Here's how to apply, what you'll need, how long it takes and what to do while you wait.3 min read · 2025/26
- What is a UTR number?A UTR (Unique Taxpayer Reference) is the 10-digit number HMRC uses for Self Assessment and Corporation Tax. Here's what it's for and personal vs company UTRs.3 min read · 2025/26
Registering & who files
Registering & who files
Do you need a return, and how to get set up.
- How to register for Self AssessmentRegister for Self Assessment by 5 October 2026 for the 2025/26 tax year. Which route to use, what you need, how long your UTR takes and what happens next.3 min read · 2025/26
- Who has to file a Self Assessment?Am I due a tax return? Common reasons you must file a Self Assessment for 2025/26 — self-employment, rental income, dividends, savings, Child Benefit charge.3 min read · 2025/26
- How to register as self-employedStarted working for yourself? How to register as self-employed with HMRC, the 5 October deadline, what you need, and what happens to National Insurance now.4 min read · 2025/26
Paying & refunds
Paying & refunds
How to pay HMRC, payments on account, plans and refunds.
- How to pay your Self Assessment tax billPay your Self Assessment bill by bank transfer, Direct Debit, card or the HMRC app. HMRC bank details, your payment reference (UTR + K) and clearing times.3 min read · 2025/26
- Payments on account explainedPayments on account are two advance payments towards next year's tax, due 31 January and 31 July. When they apply, examples, and how to reduce them.3 min read · 2025/26
- Self Assessment payment plans (Time to Pay)Can't pay your tax bill? How to set up a Self Assessment payment plan with HMRC: who can apply online, what you need and how interest works.3 min read · 2025/26
- How to claim a Self Assessment tax refundOverpaid through Self Assessment? How tax refunds work after you file, how to claim one in your HMRC account and how long it takes to arrive.3 min read · 2025/26
Deadlines & dates
Deadlines & dates
Tax year dates and the deadlines that matter.
Penalties
Penalties
What late filing and late payment really cost.
Expenses & allowances
Expenses & allowances
What you can claim, and the £1,000 allowances.
- Allowable expenses for the self-employedWhat can you claim as self-employed? Allowable expenses checklist: office, travel, stock, phone, working from home, staff and more — and what HMRC won't allow.3 min read · 2025/26
- The £1,000 trading allowanceEarn under £1,000 from a side hustle and you may not need to tell HMRC. How the trading allowance works, when to register and platform reporting.3 min read · 2025/26
- SA103: the self-employment pagesSA103 is where sole traders report self-employment income on the tax return. Short vs full pages, what goes in each section, and the figures you'll need.3 min read · 2025/26
Landlords & CIS
Landlords & CIS
Rental income and construction subcontractors.
- Rental income tax for landlordsHow rental income is taxed in the UK: the £1,000 property allowance, allowable costs, Section 24 mortgage interest relief and reporting it on your tax return.3 min read · 2025/26
- CIS tax refunds for subcontractorsCIS subcontractors often overpay because 20% is deducted from gross pay. How a CIS tax refund works through Self Assessment and when you get it.3 min read · 2025/26
Gig work & selling online
Gig work & selling online
Drivers, riders and online sellers: what to declare and claim.
- Self Assessment for Uber driversTax for Uber and private hire drivers: registering as self-employed, what counts as income, mileage vs actual car costs, and filing your Self Assessment.4 min read · 2025/26
- Tax for Etsy and online sellersSelling on Etsy, eBay or Vinted? When it's a hobby vs a business, the £1,000 trading allowance, platform reporting to HMRC, expenses and filing a tax return.4 min read · 2025/26
Tax codes, letters & HMRC login
Tax codes, letters & HMRC login
Read your tax code, check HMRC letters and get signed in.
- Tax codes explainedWhat your tax code means and how to check it's right. 1257L, the letters L, M, N, T, BR, D0, 0T, NT and K codes, and how to get a wrong tax code fixed.5 min read · 2025/26
- Emergency tax codesOn an emergency tax code like 1257L W1, M1 or X? Why it happens, why you might pay too much tax, how to get it fixed and how to claim the overpayment back.3 min read · 2025/26
- HMRC letters about savings interestGot an HMRC letter or tax code change for savings interest? How the Personal Savings Allowance works, Simple Assessment letters, and what to check before you pay.4 min read · 2025/26
- Government Gateway & HMRC sign-inHow signing in to HMRC online services works: Government Gateway user IDs, GOV.UK One Login, the HMRC app, what to do if you're locked out, and staying safe.3 min read · 2025/26
Making Tax Digital
Making Tax Digital
The new quarterly rules for Income Tax.
Choosing how to file
Choosing how to file
Accountant, software or DIY.
Your tax return isn't going to do itself.
Actually, TaxGo gets pretty close.