Self-Assessment Tax Return

Self Assessment is how HM Revenue & Customs (HMRC) collects Income Tax from people with income that isn’t fully taxed at source. If all your tax is handled via PAYE you might not need a return, but many people do. We can prepare and file your return accurately and on time, handle HMRC correspondence, and advise on payments and refunds.

Who must send a tax return

You must file a return for the last tax year (6 April to 5 April) if any of the following apply:

  • You were self-employed (sole trader) and your gross trading income was over £1,000.

  • You were a partner in a business partnership.

  • You had to pay Capital Gains Tax (for example after selling shares or a second home).

  • You (or your partner) claimed Child Benefit and the higher earner’s income was over £60,000 in 2024/25 (the High Income Child Benefit Charge now tapers away between £60,000 and £80,000).

  • You had untaxed income such as rent, tips/commission, savings interest, dividends or foreign income. (HMRC lists these as common reasons.)

  • Your employment expenses to claim are over £2,500 in a year (claims above this level must be done via Self Assessment).

Company directors: being a director doesn’t automatically mean you must file—but you may need to if you receive untaxed income (e.g., dividends).

Savings/dividends: if you don’t normally complete a return and your total savings income is £10,000 or more, you must register and file a Self Assessment return.

If HMRC has told you to file, you must send a return even if you have no tax to pay.

Key deadlines for the 2024/25 tax year

  • Register for Self Assessment: 5 October 2025 (if you need to file and haven’t registered before).

  • Paper return deadline: 31 October 2025 (11:59pm).

  • Online return deadline: 31 January 2026 (11:59pm).

  • Payment deadline: 31 January 2026 (and 31 July for the second “payment on account”, if applicable).

Payments on account: HMRC will normally ask for two advance payments towards next year’s bill (31 January and 31 July), based on your previous liability. You can view or reduce payments on account through your HMRC online account if your current year’s income is lower.

Penalties & interest (latest HMRC figures)

Late filing penalties (miss the filing deadline and):

  • Immediate £100 fixed penalty.

  • After 3 months: £10 per day (up to £900).

  • After 6 months: an extra 5% of tax due or £300 (whichever is greater).

  • After 12 months: another 5% or £300 (whichever is greater).

Late payment penalties (miss the payment deadline and):

  • 5% of the unpaid tax at 30 days, another 5% at 6 months, and another 5% at 12 months, plus interest.

If you have a reasonable excuse, you can appeal a penalty.

CIS (Construction Industry Scheme) – subcontractors

Under CIS, contractors deduct tax at source from subcontractors and pay it to HMRC. The standard deduction is 20% for registered subcontractors and 30% if you’re not registered or can’t be verified. With gross payment status, no deduction is made (0%) and you pay tax through Self Assessment at year end. Keep your monthly payment & deduction statements for your return.

What we need to get started

  • UTR and National Insurance number

  • P60/P45, P11D (benefits), student loan details (if any)

  • Business income & expense records (or CIS statements)

  • Bank interest and dividend summaries

  • Property income & expenses

  • Details of pension contributions, Gift Aid, Child Benefit, foreign income, and any capital asset disposals

How we help

We’ll register you (if needed), prepare and submit your return, check your tax position (including payments on account), deal with HMRC, and advise on reliefs and allowances so you don’t overpay.