The 31st January Self Assessment deadline is approaching, and if you haven’t started preparing your tax return yet, you’re not alone.
Whether you’re a limited company director, sole trader or someone with additional personal income to declare, leaving everything until the last minute can make the process more stressful than it needs to be. From gathering the right financial records to understanding what you might owe, a little preparation now can help you avoid unnecessary complications and stress later.
Here is what you need to get it done without the panic.
What Does the 31st January Deadline Mean?
The 31st January 2027 is the deadline for submitting your online Self Assessment tax return for the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026.
It’s also the deadline for paying any outstanding Self Assessment tax due for that year.
Depending on your circumstances, this could include:
- Balancing payment: Any remaining tax owed for 2025/26 after accounting for payments already made.
- First payment on account: An advance payment towards your 2026/27 tax liability, if payments on account apply to you.
Payments on account can sometimes catch people by surprise, particularly if they’re completing their first Self Assessment return. Not everyone is required to make them, so it’s worth checking your individual position rather than assuming the amount due will simply be your outstanding tax for the previous year. The earlier you understand what you owe, the more time you’ll have to prepare financially.
1. Make Sure You Have Your HMRC Details
Before you can submit your return, you’ll need access to the relevant HMRC information.
If you’re filing yourself, this will usually include your Unique Taxpayer Reference (UTR) and Government Gateway login details.
Your UTR is a 10-digit reference issued by HMRC when you register for Self Assessment. You may be able to find it on previous tax returns, correspondence from HMRC or within your online tax account.
If you’ve misplaced your details, it’s worth sorting this out sooner rather than later.
If you’re using an accountant, they’ll need the appropriate authorisation and relevant information from you to prepare and submit your return.
2. Gather the Right Financial Records
Filing a tax return isn’t guesswork. You need documentation for everything you’re declaring, and HMRC can ask to see it later, so don’t discard anything yet. The information you need will depend on how you earn your income.
For Limited Company Directors
If you’re a director of a limited company, your personal tax return may need to include several different sources of income.
These could include:
- Salary and employment income: Your P60 or P45, along with details of any taxable benefits reported on a P11D.
- Dividends: Records of dividends received from your limited company, including dividend vouchers.
- Savings and investments: Bank interest, investment income and dividends from shares outside your company.
- Other personal income: Rental income, capital gains or other income that needs to be declared.
Remember, being a company director doesn’t automatically mean you need to submit a Self Assessment return. Your requirement to file will depend on your circumstances and whether HMRC has issued a notice to file.
For Sole Traders
If you’re self-employed as a sole trader, you’ll generally need accurate records of your business income and allowable expenses.
These could include:
- Sales invoices and records of business income
- Business bank statements
- Receipts for allowable expenses
- Records of business mileage and travel
- Details of equipment or other business purchases
- Any other income that needs to be declared
Sole traders generally need to register for Self Assessment if their gross trading income exceeds £1,000 in a tax year, although other circumstances can also create a filing requirement.
It’s also worth remembering that being a sole trader doesn’t mean self-employment is your only source of income. If you’re employed alongside running your business, you may also need your P60 or P45, along with details of any taxable employment benefits.
Similarly, if you receive dividends, savings interest, rental income or other taxable income, you’ll need to consider these when completing your Self Assessment return. Make sure you review all your sources of income, not just what you’ve earned through your business.
Having your records organised before you begin will make completing your return much easier.
3. Check Your Records Before You Start
Having the right documents is one thing. Making sure the information is accurate is just as important. Before completing your return, take some time to check that your records are consistent and nothing has been overlooked.
For limited company directors, this might mean checking that your dividend records match the amounts you’ve received and that all relevant sources of personal income have been included.
For sole traders, it could mean reviewing business income, checking expenses have been recorded correctly and making sure your bank transactions reconcile with your bookkeeping records.
It’s much easier to resolve any questions before submitting your return than to discover an error afterwards. While HMRC permits estimates in certain circumstances, you shouldn’t simply guess figures because you’re running out of time.
4. Don’t Leave Filing Until the Last Minute
Even when your records are organised, completing a tax return can take longer than expected. There may be information you need to clarify, calculations to check or additional documentation to obtain.
If you’re filing through HMRC’s online service, particularly for the first time, give yourself enough time to work through each section carefully. Don’t attempt to complete your tax return 20 minutes before the deadline when you’re tired and stressed. The system saves your progress as you go, so you don’t have to compete it all in one sitting. Double-check figures and take breaks if you need to. If something doesn’t make sense, look it up or ask someone who knows, because fixing errors after submission is a hassle you don’t need.
If you’re using an accountant, remember they’ll need time to prepare your return, review the information and obtain your approval before submission.
Submitting earlier also means you’ll know what your tax bill looks like before the payment deadline, giving you more time to manage your cash flow.
5. Understand What Happens If You Miss the Deadline
Missing the Self Assessment filing deadline can result in an initial £100 late filing penalty, even if you have no tax to pay.
Further penalties can apply if your return remains outstanding, while late payment can lead to interest and additional charges. If you’re concerned about being unable to pay your tax bill, don’t ignore it.
HMRC may offer a Time to Pay arrangement to eligible taxpayers, allowing an outstanding liability to be paid in instalments. It’s worth exploring your options as early as possible rather than waiting until the payment deadline has passed.
6. Understand How Making Tax Digital Could Affect You
For Limited Company Directors
If you receive a salary and dividends from your limited company, this income alone doesn’t bring you into Making Tax Digital (MTD) for Income Tax. However, if you also have qualifying self-employment or property income, you may need to consider whether the requirements apply to you personally.
Your limited company’s Corporation Tax obligations remain separate from your personal Self Assessment responsibilities.
For Sole Traders
From 6 April 2026, Making Tax Digital for Income Tax became mandatory for eligible sole traders and landlords with qualifying income over £50,000, based on the relevant previous tax return. Further thresholds are being introduced in subsequent years.
Those within the requirements must use compatible software to maintain digital records and send quarterly updates to HMRC throughout the year, alongside completing the required year-end reporting. If you haven’t already, now is a good time to check when the requirements will apply to you and whether your bookkeeping systems are ready. Even if that doesn’t apply to you yet, getting your records organised digitally now will make your future filing easier.
You can find further information on the GOV.UK website.
Need Help Preparing for the Self Assessment Deadline?
The 31st January deadline doesn’t need to become a last-minute rush. Getting your records together early, understanding your tax position and allowing enough time for your return to be prepared can make the process much more manageable.
At BW Business Accountants & Advisers, we specialise in supporting UK limited companies and their directors with their accounting and tax responsibilities. We help our clients understand their obligations, prepare for upcoming tax liabilities and make informed financial decisions throughout the year.
If you’re a limited company director looking for proactive accounting and tax support, get in touch with our team to discuss how we can help. See what services and packages we provide here.
Looking to reduce your Corporation Tax bill before year-end? In this guide, we cover key areas to check before year-end helping you make informed decisions and avoid paying more Corporation Tax than necessary.
Disclaimer: The information mentioned in this blog was correct at the time of posting (November 2026) and has not been updated for any future changes in tax law or HMRC practice. The contents of this blog has been produced as a helpful reference point, and the information provided should be used as a guide only. You should discuss your specific circumstances directly with us before taking any action based on the information included in this blog.