Key deadline: online Self Assessment returns are normally due by 31 January following the end of the tax year, with tax due on the same date. Earlier registration and record-keeping deadlines can also apply.
Who needs to register?
If you start trading as a sole trader and meet the relevant Self Assessment criteria, you need to tell HMRC and obtain the appropriate tax registration. Do not wait until January to start the process.
What records should you keep?
- Sales and other business income.
- Business expenses and receipts.
- Bank and card records.
- Vehicle/mileage evidence where relevant.
- CIS statements if you are a subcontractor.
- Details of other personal income needed for the return.
How is the tax calculated?
Broadly, allowable expenses are deducted from business income to arrive at taxable business profit, which is then considered with your other income, allowances and relevant National Insurance rules.
What are payments on account?
Payments on account are advance payments towards the following year's Income Tax liability. They can make the first substantial January payment feel much larger because a balancing payment and the first payment on account can fall together.
Why file early?
Filing early does not normally mean paying earlier, but it tells you the liability sooner, gives time to correct missing records and makes cash-flow planning easier.
MTD is changing the process
From April 2026, some sole traders are already within Making Tax Digital for Income Tax, requiring digital records and quarterly updates in addition to the year-end process.
Frequently asked questions
When is the online tax return due?
The usual online filing deadline is 31 January following the end of the tax year.
Do I have to pay tax when I file early?
Filing early does not normally move the statutory payment deadline forward.
What if I am in CIS?
CIS deductions suffered are relevant to your tax calculation, so keep all contractor payment and deduction statements.