The January problem
The 31 January 2027 deadline is not a comfortable horizon. By the time Christmas and New Year are factored in, the effective working window between now and the deadline is considerably shorter than it appears. Many accountants are operating at capacity from mid-December onwards, meaning that clients who come to them in January receive less time and attention than those who engage earlier.
There is also the matter of what the January deadline actually involves. It is not simply a filing deadline — it also covers payment of your balancing tax liability for 2025/26 and, for many taxpayers, a first payment on account for 2026/27. Discovering in January that you owe a substantially larger amount than anticipated is stressful, and avoidable.
Why November specifically?
November is genuinely one of the best months to start. The tax year ended on 5 April 2026, which means all the information needed for your return already exists. P60s have been issued. Business records cover the full year. Bank statements are available. There is nothing to wait for — it is simply a matter of gathering and submitting.
Acting in November also gives you time to:
- Know your exact tax liability before the Christmas period, so you can plan your cash flow accordingly
- Identify any reliefs or allowances you may have overlooked — something that is difficult to do under deadline pressure in January
- Make a payment on account reduction application if your income in 2025/26 was lower than the previous year
- Avoid the HMRC online filing rush in January, when the system experiences its highest volumes and occasional technical difficulties
A note on the 30 December deadline
There is a lesser-known Self Assessment deadline on 30 December 2026 that is relevant to many employed taxpayers who also file a Self Assessment return. If you file your 2025/26 return online by 30 December and you owe less than £3,000, HMRC can collect the underpayment through your 2027/28 PAYE tax code rather than requiring a lump-sum payment. For taxpayers who would prefer to spread their liability, this is a genuinely useful option — but it requires the return to be filed a full month before the standard deadline.
What information do you need?
Most Self Assessment returns require some combination of the following:
- P60 or P45 from any employment in 2025/26
- Records of self-employment income and business expenses
- Rental income and allowable property expenses
- Dividend vouchers and bank interest statements
- Details of any capital disposals — property, shares, or other assets
- Pension contribution records and Gift Aid donation receipts
If you have been filing quarterly MTD for Income Tax updates since April 2026, much of the underlying data will already be captured in your accounting software. Your accountant will still need to prepare the End of Period Statement and Final Declaration to complete the process.
One last thought
Filing early does not just mean less stress. It means better advice, more time to act on planning opportunities, and the peace of mind of going into Christmas knowing exactly where you stand financially.
Ready to get your 2025/26 Self Assessment done before Christmas? Get in touch with our South Wales team today — the sooner you start, the smoother it will be. Call us on 01443 834047, or email info@fooks.co.uk to get the ball rolling.
