Are you a company director, founder or self-employed business owner preparing for a UK Self Assessment tax return? The January deadline can feel distant : until an overlooked dividend, Child Benefit charge or payment on account turns into an expensive surprise.
For the 2025/26 tax year, HMRC must receive your online return and payment by 11:59pm on 31 January 2027. If you need to register for Self Assessment for the first time, the deadline is 5 October 2026.
And there is another date to keep firmly on your radar: 31 July 2027, when the second payment on account may be due.
Getting your tax return right is not just about avoiding a penalty. It is about paying the right amount of tax, protecting your personal cash flow and keeping your financial affairs clear as your business grows.
Important date clarification: the 2026/27 tax year runs from 6 April 2026 to 5 April 2027. The online filing deadline for that tax year is normally 31 January 2028. However, many business owners searching for the “Self Assessment deadline 2026” are preparing the 2025/26 return due in January 2027.
The following dates relate to the 2025/26 tax year, which ended on 5 April 2026:
For the 2026/27 tax year, the equivalent online filing and payment deadline is 31 January 2028.
You can check the latest dates on HMRC’s Self Assessment deadline guidance.
You may need to file a Self Assessment tax return if you:
Being a director does not automatically mean you must file a tax return. But directors commonly need to report dividends, benefits in kind, investment income or other personal income.
If you are uncertain, use HMRC’s Self Assessment checker or speak to an adviser before the registration deadline.
For England, Wales and Northern Ireland, the standard 2026/27 income tax structure is:
The Personal Allowance is gradually reduced when your adjusted net income exceeds £100,000 and is fully withdrawn at £125,140.
Dividend income is taxed separately, although your total income determines which dividend rate applies. For 2026/27:
These rates apply to dividends above the allowance. Scotland has different income tax bands for non-savings and non-dividend income, but dividend tax rates are generally UK-wide.
You can check the current figures on HMRC’s Income Tax rates guidance and dividend tax guidance.
This is one of the most common mistakes for limited company directors.
Your company may have prepared accounts and paid Corporation Tax, but that does not mean the personal tax position is complete. Dividends are received by you personally and may need to be declared on your Self Assessment tax return.
Make sure you reconcile:
There is a common misconception that dividends are “already taxed”. In reality, the company and the shareholder have separate tax positions. The company pays Corporation Tax on its profits, whilst you may have personal dividend tax to pay when funds are distributed.
If you or your partner receives Child Benefit and your adjusted net income is above £60,000, you may have to repay some of it through the High Income Child Benefit Charge.
At adjusted net income of £80,000 or more, the charge can equal the full amount of Child Benefit received.
The calculation includes taxable income such as:
Certain reliefs, including gross pension contributions and Gift Aid donations, can reduce adjusted net income. Student loan repayments do not reduce it.
The charge is based on the higher earner’s income, not necessarily the person who receives the Child Benefit. You can read more in HMRC’s Child Benefit tax charge guidance.
Student loan repayments can appear on your Self Assessment calculation, but they are not a deduction that reduces your taxable income or adjusted net income.
If you are self-employed or have other income, HMRC may calculate your student loan repayment alongside your Income Tax and National Insurance liabilities. You need to provide the correct loan plan details and relevant income information.
Do not reduce your profits or salary simply because student loan repayments have been made. Doing so can understate your income and create an incorrect return.
If you are unsure which plan applies, check HMRC’s student loan repayment guidance and your Student Loans Company records.
Cryptoassets are not outside the tax system.
Selling, swapping, spending or gifting cryptoassets can be a disposal for Capital Gains Tax purposes. A taxable gain may need to be reported through Self Assessment, even if you have not withdrawn the money to your bank account.
Keep records of:
Capital gains are generally separate from income for adjusted net income purposes. However, crypto activity that amounts to trading or another form of taxable income may be treated differently.
HMRC’s Cryptoassets Manual explains the relevant tax treatment. The key is to keep complete records rather than relying on an exchange’s annual summary.
Self Assessment is not usually based simply on the money that entered your business bank account.
For a sole trader, taxable profit is generally calculated from business income less allowable business expenses, with adjustments where required. For a company director, your personal return may include salary, dividends, benefits and other personal income : not the company’s entire turnover.
Common errors include:
A clean bookkeeping system makes this far easier. Our Bookkeeping and Accounting service helps business owners keep financial records organised throughout the year, rather than rebuilding everything before January.
Your January bill may be larger than expected because it can include both:
The second payment on account is normally due on 31 July.
For example, a business owner with a growing dividend income may pay tax on 2025/26 income in January 2027, alongside an advance payment towards 2026/27. This can create a significant cash-flow challenge if you have only budgeted for the first liability.
Payments on account are generally based on your previous Self Assessment liability, although there are circumstances where they may not apply. We encourage you to forecast your personal tax position well before January so you can keep a tight grip on cash.
HMRC’s late filing penalties can include:
Late payment can also trigger penalties of 5% of unpaid tax at 30 days, six months and 12 months, together with interest.
A reasonable excuse may allow you to appeal, but it is far safer to file accurately and pay on time. You can review the rules in HMRC’s Self Assessment penalties guidance.
A well-prepared Self Assessment tax return gives you more than compliance. It gives you visibility.
You can:
This is where professional support can make a pivotal difference. At Price & Accountants, we help directors, founders and growing business owners prepare personal tax returns, review dividend and remuneration records, assess payments on account and identify potential tax-planning opportunities.
Our Advisory and Tax Planning service is designed to help you pay the right amount of tax : not simply complete a form at the last minute. You can also explore our Ultimate Tax Savings Guide for 2026/27 for practical planning ideas.
The January Self Assessment deadline is fixed. Your preparation does not need to be rushed.
If you are preparing a 2025/26 Self Assessment tax return, unsure whether you need to register by 5 October 2026, or concerned about dividends, Child Benefit, cryptoassets or payments on account, contact Price & Accountants for a consultative review. We can help you get on the right track, avoid expensive mistakes and move forward with greater financial clarity.
