If you’re a limited company director, you may need to sit down and get to grips with your Self Assessment tax return (SATR) before 31st January each year. Unsurprisingly, this annual task is rarely a popular one, and errors are easy to make if you’re unprepared.
In this article, we highlight some common SATR mistakes to avoid by focusing on the ‘what not to do’ when it comes to filing your return.
Inaccurate figures
If you are submitting your return yourself, you should double-check all the figures you use – typically your salary, dividend and ‘other income’ data. If your accountant files on your behalf, you are still ultimately responsible for the accuracy of the data, so check the draft SATR before signing off.
You should never deliberately record inaccurate figures, as this could lead to significant penalties. Even genuine mistakes can cause problems if HMRC decides you haven’t taken reasonable care.
Missing the filing deadlines
After filling in all your details, don’t forget to press ‘send’! Government systems let you save your form and return to it later, but you must ensure you don’t forget and miss the deadline.
You have until 31st January after the tax year ends to submit online, but failing to do so promptly could result in penalties. For the 2025/26 tax year, for example, the online deadline is 31st January 2027.
The 31st January is also the deadline to pay any outstanding tax for the previous tax year, along with your first payment on account for the current tax year, if applicable.
HMRC charges an initial £100 penalty for filing late, even if you have no tax to pay. Further penalties can follow if the return remains outstanding. If you make payments on account, don’t forget that the second instalment is due on 31st July.
For more information on deadlines and the penalties for missing them, visit this HMRC page.
Not dating and signing!
If you’re one of the minority who still submit a paper return, you might be in a rush to get it sent off in order to beat the deadline (31st October), but whatever you do, don’t forget to sign and date the document, as failure to do so could result in the invalidation of the form.
If you’re filing online, make sure you complete the submission process and receive confirmation. Saving your return for later won’t count as filing it.
Missing supplementary pages
You are often required to complete supplementary pages or additional sections of your tax return to include information which is not covered by the main form, so don’t overlook these. Depending on your circumstances, these can include:
- Interest from gilt-edged and other UK securities, deeply discounted securities and accrued income profits.
- Life insurance gains.
- Stock dividends, certain other distributions and loans written off.
- Income from property or self-employment.
- Share schemes, employment lump sums or compensation payments from a previous employer.
- Capital gains and certain foreign income.
- Other tax reliefs, for example if you’ve invested in Venture Capital Trust schemes or EIS.
Not everyone needs supplementary pages, but if you have income beyond your usual salary and dividends, check whether you need an additional section.
Mis-recorded Unique Taxpayer Reference (UTR) or NI number
You could have problems with your SATR if you record your UTR or National Insurance number incorrectly.
You can find your personal UTR on previous correspondence from HMRC or through your online tax account if you have previously registered for Self Assessment. If not, you may need to register for Self Assessment before submitting your first return.
Your NI number will have been issued to you when you started working (and will be present on any number of old tax documents in your possession).
If you’re a company director, remember that your personal UTR is different from your company’s Corporation Tax UTR. It’s surprisingly easy to confuse the two if you have a pile of HMRC correspondence in front of you.
Failure to declare all income
Whether it is taxable income or capital gains, you must declare the amounts that are required to be reported on your tax return. Not every dividend, savings interest payment or capital gain needs to be reported, as exemptions, allowances and reporting thresholds may apply. If you omit information that should have been included, you could face penalties, particularly if you are subsequently found to have deliberately under-represented your income.
Depending on your circumstances, the following types of income may need to be declared:
- Salary from employment during the year.
- Dividend income.
- Taxable Government benefits.
- Income from pensions.
- Income from letting out properties.
- Interest on savings.
- Foreign income (you will need proof if tax has already been paid overseas).
- Employee share schemes.
- Capital gains where reporting is required.
Certain types of income do not normally have to be reported, including interest earned within ISAs and Premium Bond winnings.
Company directors should also check whether they have any taxable benefits in kind or directors’ loans to report, as these can easily be overlooked.
If you’re unsure about a particular source of income, check with your accountant before submitting the return.
Poor record-keeping
Keep all relevant paperwork in a safe place, so you have everything you need to complete your SATR accurately.
Here is a list of some typical documents a limited company director may need:
- Salary and benefit-related HMRC paperwork, including P60, P11D and P45.
- Records of any student loan payments made.
- Records of any payments into a pension scheme.
- Records of payments into an employee share scheme.
- Details of income derived from property, such as rents and allowable expenses.
- Details of Child Benefit received, where relevant.
- Bank statements showing any interest paid.
- Details of charitable gifts made during the tax year, to claim tax relief.
- Dividend vouchers from your own company and any others.
Gathering these details in advance will save a lot of time when you or your accountant prepare the return. Also check that the dividend figures match your company’s records, particularly if you took money out of the company at irregular intervals during the year.
Making Tax Digital for Income Tax came into force in April 2026 for sole traders and landlords with annual gross income of more than £50,000 from these sources. Those affected must keep digital records and send quarterly updates to HMRC. The limit falls to £30,000 in April 2027 and £20,000 in April 2028. If you simply receive a salary and dividends from your limited company, these rules won’t affect you.
