2025/26 online filing deadline
The deadline for filing an online Self Assessment return for 2025/26, and normally paying the tax due for that return, is 31 January 2027. Your exact obligations depend on HMRC rules and your circumstances.
Clear UK Self Assessment Tax Return Support
Taxnex supports the preparation of HMRC Self-Assessment information—from organising business expenses to calculating the tax position and explaining the submission steps and statutory deadlines.
Who Must File a UK Self-Assessment Return?
You are required to submit an SA100 Self-Assessment tax return if in the last tax year (6 April to 5 April):
- Your gross self-employment earnings exceeded £1,000 (the trading allowance).
- You were a partner in a business partnership.
- You received taxable income from renting out UK or overseas property exceeding £2,500.
- You earned taxable dividends or investment income above statutory allowances.
- Your total taxable income exceeded £100,000 (or £150,000 for recent rules).
- You were subject to the High Income Child Benefit Charge (where you or your partner earned over £50,000 / £60,000).
- You sold capital assets (shares, second homes, crypto) and incurred Capital Gains Tax liability.
Key Self-Assessment Deadlines You Must Know
| Milestone | Statutory Deadline | What Needs to Be Done |
|---|---|---|
| Register for Self-Assessment | 5 October following tax year | Register with HMRC to obtain your 10-digit Unique Taxpayer Reference (UTR). |
| Paper Tax Return Filing | 31 October following tax year | Physical paper SA100 forms submitted to HMRC. |
| Online Return & Tax Payment | 31 January following tax year | Final deadline for digital submission and paying your balancing tax bill + 1st Payment on Account. |
| Second Payment on Account | 31 July following tax year | Second advance payment towards the current year’s tax liability. |
Allowable Expenses: Maximising Your Legitimate Deductions
We review the records supplied and identify categories of potentially allowable business costs, which may include:
- Vehicle & Travel: For 2026/27, simplified mileage for eligible cars and goods vehicles is 55p for the first 10,000 business miles and 25p thereafter, or actual vehicle running costs (fuel, insurance, repairs, MOT, finance interest).
- Working from Home: HMRC flat rate simplified expenses or apportioned household utility bills.
- Office & Tools: Phone bills, broadband, software subscriptions, tools, equipment, and stationery.
- Professional Costs: Accountancy fees, professional body memberships, trade insurance, and banking charges.
How Our Self-Assessment Service Works
- Step 1 — Initial Discussion & Quotation: We discuss your requirements and provide a tailored quotation for review.
- Step 2 — Document Sharing: If you proceed, Taxnex provides instructions for supplying the records required for the agreed work.
- Step 3 — Calculation & Review: We calculate your exact tax position, explain any Payments on Account, and send the completed return for your digital approval.
- Step 4 — Submission Support: The applicable filing arrangement and responsibilities are confirmed with you during onboarding.
Please do not submit confidential financial details (such as your UTR, National Insurance number, online banking passwords, or identity documents) through general website forms. Secure, encrypted document exchange instructions will be provided after initial consultation.