The 31 January deadline comes round quickly, especially with Christmas in between. If you’re a sole trader or landlord in Sevenoaks, Kemsing or elsewhere in West Kent, this guide covers what you need to do for the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026. It also explains how to avoid a penalty.

Who needs to file a 2025/26 tax return?

You’ll usually need to send a Self Assessment tax return for 2025/26 if, in that year, you:

  • were self-employed as a sole trader and earned more than £1,000 before expenses
  • were a partner in a business partnership
  • received rental income from a property, including letting a flat or house in Sevenoaks or further afield, above the £1,000 property allowance
  • had other untaxed income, such as significant savings or investment income, foreign income or capital gains that need reporting
  • received a letter or notice from HMRC asking you to file

If you’re unsure, HMRC has a checker on GOV.UK, or you can ask us and we’ll look at your situation.

Missed the 5 October registration deadline?

If you needed to file for the first time for 2025/26, perhaps because you started a business or began letting a property, you should have registered for Self Assessment by 5 October 2026. If you missed that date, register as soon as you can. HMRC sends a Unique Taxpayer Reference (UTR) by post, and that can take a while, so it’s best not to leave it until January.

31 January 2027: file and pay

For the 2025/26 tax year:

  • the deadline for filing your return online is midnight on 31 January 2027
  • any tax you still owe for 2025/26 must be paid by 31 January 2027
  • your first payment on account for 2026/27, if you need to make one, is also due by 31 January 2027

The paper return deadline (31 October 2026) has already passed, so most people will now file online.

Payments on account explained

Payments on account are advance payments towards next year’s tax bill. They catch many people out in their second year of trading or letting, when the January bill can seem much bigger than expected.

  • Each payment is normally half of your previous year’s Self Assessment bill.
  • They’re due by 31 January and 31 July.
  • You don’t have to make them if your last bill was under £1,000, or if more than 80% of your tax was already collected at source, for example through PAYE.
  • If you expect your income to fall, you can ask HMRC to reduce them. If you reduce them too far, though, you’ll be charged interest on the shortfall.

Penalties and interest

If your return is late, HMRC’s penalties under the current rules are:

  • £100 straight away, even if you owe no tax
  • after 3 months, £10 a day for up to 90 days
  • after 6 months, a further £300 or 5% of the tax due, whichever is higher
  • after 12 months, another £300 or 5%, or more in some cases

If you pay late, interest is charged from the day after the deadline. Late payment penalties of 5% of the unpaid tax can also apply at 30 days, 6 months and 12 months. If you can’t pay in full, contact HMRC early, because a Time to Pay arrangement may be possible.

Your Self Assessment checklist

  • Your UTR and Government Gateway login
  • Your sales or turnover and business expenses for 6 April 2025 to 5 April 2026
  • Rental income, letting agent statements and allowable property costs
  • Mortgage interest statements for any let property
  • P60 or P45 if you were also employed, and any P11D
  • Bank and building society interest, and dividend vouchers
  • Pension contributions and Gift Aid donations
  • Details of any assets sold, such as shares or a second property
  • Student loan and Child Benefit details, if relevant

Get ahead with Making Tax Digital

If your combined income from self-employment and property was over £50,000 in 2024/25, Making Tax Digital for Income Tax already applies to you from April 2026. The threshold falls to £30,000 from April 2027. Your 2025/26 return is the one HMRC will use to check whether you’re in scope next, so now is a good time to get your records in order.

Let Coplestons take care of it

We’re a local practice based in Kemsing and we help sole traders and landlords across Sevenoaks and West Kent with their tax returns every year. Send us your paperwork and we’ll prepare your return, check it with you and file it well before the deadline, so you know what you owe in good time.

Call us on 01732 762886, email info@coplestonsaccountants.com or get in touch through our contact page. You can also see our services. We’re open Monday to Friday, 9am to 5pm, at Suite 2, 9 West End, Kemsing, Sevenoaks, Kent TN15 6PX.