How to file a Self Assessment tax return online

You must send a return if HMRC tells you to, or if you have untaxed income (for example self-employment, UK property, dividends/interest, foreign income, capital gains, Child Benefit high-income charge, etc.). If you’re unsure, use HMRC’s checker and guidance.

New to SA? Tell HMRC by 5 October (register for Self Assessment to get your UTR).

Have these to hand before you start:

• Your UTR, National Insurance number, and Government Gateway sign-in.
• Income details (P60/P45, P11D, bank interest, dividends, pensions).
• If relevant: self-employment figures, UK property totals, capital gains (dates, proceeds, costs), foreign income.
• Reliefs/claims: pension contributions, Gift Aid, student loan plan type, marriage allowance.

This prep makes the online form faster and reduces mistakes. HMRC explains the online journey step-by-step.

If you haven’t filed online before, set up an HMRC online account and activate it (allow time for codes to arrive). Existing users can sign in and start their return immediately.

Filing online is secure, available 24/7 and gives instant confirmation that HMRC received your return.

With Ftax, you complete the familiar SA100 layout in clear, plain English. Based on simple prompts, we switch on only the sections you need (employment, self-employment SA103, property SA105, foreign income SA106, capital gains SA108, and more). Built-in checks highlight missing info before you submit, helping you avoid rejections and amendments later.

Helpful routes from here:

• New filer? See our Self Assessment Hub for step-by-steps and examples.
• Landlords / Sole Traders / Investors / Expats? Visit the pages for tailored guidance before you fill in the relevant sections.

When your figures are ready:

• Run validation checks in Ftax to catch typos and gaps.
• Authorise submission with your Government Gateway sign-in.
• Submit from Ftax and keep the HMRC receipt as proof of delivery.

You’ll see your tax calculation so you know what’s due and why. (If you later discover an

• Pay by 31 January (and 31 July if Payments on Account apply). HMRC details how
• If HMRC estimates you’ll owe tax in the current year, you may be asked for Payments on Account—two instalments towards this year’s bill (January and July).
• Refund due? You can request repayment as part of filing or via your HMRC account.

• 5 October: deadline to register if you need to start filing Self Assessment.
• 31 October: deadline for paper returns (most people file online).
• 31 January: online filing deadline and payment deadline for the tax year that ended the previous 5 April.
• 31 July: second Payment on Account (if applicable).

HMRC encourages early filing to avoid last-minute pressure and to spread payments with better planning.

MTD for Income Tax will introduce quarterly updates for many sole traders and landlords in phased stages (with end-of-year finalisation). Get familiar with the roadmap and keep digital records early—it makes the switch easier. See our MTD hub and HMRC’s latest guidance on timelines and who’s in scope.

• HMRC-recognised submission, with an HMRC receipt every time.
• Plain-English guidance alongside the real SA100 pages.
• Focused workflow, only the sections you need, with built-in validation.
• Built for individuals, business filers and agents, with clear upgrade paths as your needs grow.