1. Confirm the tax year and your deadlines
This return covers 6 April 2025 to 5 April 2026. The normal paper filing deadline is 31 October 2026; the online filing and tax payment deadline is 31 January 2027. If you want eligible tax collected through your PAYE code, the online submission deadline is 30 December 2026, subject to the collection conditions.
The usual notification date of 5 October 2026 has passed. If you should have registered, act now. A late-issued notice can give a different filing date, but does not automatically postpone the tax payment date. Check HMRC's actual notice.
2. Build one complete information pack
Our practical starting point is a folder for the tax year, with a short note explaining what changed. Include the documents relevant to your circumstances:
- Employment and pensions: P60s, P45s, benefit information, pension statements and details of tax already deducted.
- Savings and investments: interest certificates, dividend statements and investment tax reports. Include accounts opened or closed during the year.
- Property: letting statements, rent schedules, expenses, mortgage interest statements and purchase or sale documents. Keep each property's records identifiable.
- Self-employment: income and expense records, bank reconciliations, asset purchases and details of the accounting period.
- Other matters: overseas income and tax, disposal proceeds and acquisition costs, personal pension contributions, Gift Aid and relevant HMRC correspondence.
This is an information checklist, not a statement that every expense is deductible. Your adviser should review the treatment, supporting evidence and reporting requirements.
3. Tell your adviser what changed
Highlight a new rental property, a business starting or stopping, changes of employment, a share sale, a move into or out of the UK, or overseas work. A bank total rarely explains the underlying tax question.
For example, a landlord's large payment could contain repairs, improvements and financing costs. Send the invoice and a short description of the work rather than labelling the whole amount as maintenance. For investments, provide acquisition history as well as sale proceeds.
Where relevant, discuss capital gains or residence and overseas income before assuming the standard return is the only reporting required.
4. Budget for the January payment, not just the annual liability
Your January payment may include the balance for 2025/26 and a first payment on account for 2026/27. Payments on account are usually two instalments, each half the previous year's relevant liability, due on 31 January and 31 July. They are normally not required if that liability is below £1,000 or more than 80% of your tax was paid outside Self Assessment.
Illustration: assume a first-time filer has £4,000 of relevant liability, no earlier payments and no amounts excluded from payments on account. January 2027 could require £6,000: £4,000 for 2025/26 plus £2,000 towards 2026/27. A further £2,000 would fall due in July 2027. These are advance payments, not a higher tax rate.
If next year's liability will be lower, review whether a reduction is justified. Reducing too far can result in interest. Reconcile the calculation to HMRC's account before paying.
5. Resolve missing information before the final week
Request duplicate statements or invoices now and keep a list of anything outstanding. HMRC distinguishes provisional figures, which you expect to confirm later, from estimates that cannot be confirmed. Where used, the return needs an explanation; these figures should not be a shortcut around obtaining available records.
Agree who will chase each missing item, when the draft will be reviewed and how approval will be recorded. Keep a copy of the submitted return, calculation and filing receipt together.
6. Arrange help with the return
UA Tax prepares Self Assessment returns for landlords, directors, professionals and individuals with UK and international tax affairs. We are based in London and serve clients throughout the UK. Personal tax services start from £400, with the fee reflecting complexity and agreed before work begins.
Get in touch about your 2025/26 return. Tell us the main income sources and any urgent deadline. We will arrange a secure route for documents after discussing the work.
For advice on your own circumstances, see our personal tax returns service and agree the scope before acting.
Official sources and further reading
These primary sources support the framework above. Check the current version before acting because tax law and HMRC guidance can change.