Self Assessment Tax Returns
We prepare and file Self Assessment tax returns for the self-employed, landlords, company directors and high earners. Accurate figures, every relief claimed, and your return filed on time so you never face an avoidable HMRC penalty.
What is Self Assessment?
Self Assessment is the system HMRC uses to collect Income Tax (and often National Insurance and Capital Gains Tax) from people whose income is not taxed automatically through PAYE. Instead of an employer deducting tax for you, you report your income and gains on a tax return each year, and HMRC calculates what you owe. The tax year runs from 6 April to 5 April, and the return covers everything earned in that period.
If most of your income already has tax deducted at source, you may never need to file. But once you have untaxed income — from a side business, property, dividends, foreign earnings or large capital gains — the responsibility shifts to you to declare it correctly and on time.
Who needs to file a tax return?
You will usually need to complete a Self Assessment return if you fall into one of these groups:
- The self-employed and sole traders with gross trading income above the £1,000 trading allowance.
- Landlords receiving rental income from UK or overseas property.
- Company directors who receive dividends or other untaxed income.
- High earners — for example those liable for the High Income Child Benefit Charge, or with total income that affects their Personal Allowance.
- Investors with significant savings interest, dividends, or capital gains to report — estimate any tax due with our free CGT calculator.
- Anyone HMRC has specifically asked to file.
If you are unsure, the safest approach is to check your circumstances against the criteria on GOV.UK or ask us — filing unnecessarily wastes time, but failing to file when required leads to penalties.
Registration and key deadlines
If this is your first year filing, you must register with HMRC by 5 October following the end of the tax year so you receive your Unique Taxpayer Reference (UTR). After that, the calendar below applies each year. Always confirm current dates on GOV.UK, as deadlines can shift around weekends and Bank Holidays.
| Deadline | What is due |
|---|---|
| 5 October | Register for Self Assessment (first-time filers) |
| 31 October (midnight) | Paper tax return submission |
| 31 January (midnight) | Online tax return & balancing payment; first payment on account |
| 31 July | Second payment on account |
Most people now file online, which gives the later 31 January deadline and an instant tax calculation. Paper filers must submit three months earlier, by 31 October.
Payments on account explained
If your tax bill is more than £1,000 and less than 80% of your tax is collected at source, HMRC asks you to make payments on account — advance payments towards next year’s bill. Each instalment is 50% of your previous year’s liability, paid on 31 January and 31 July. The following January, a balancing payment corrects any over- or under-payment. This often surprises first-time filers, who can face roughly 150% of their tax in one January payment. We forecast this in advance so there are no nasty cash-flow shocks.
Allowable expenses and reliefs
Claiming the right expenses is where good accounting earns its fee. The self-employed can deduct costs incurred wholly and exclusively for the business: office and stationery, business travel and mileage, stock and materials, professional and accountancy fees, insurance, and a fair proportion of home-working costs. Landlords can deduct letting agent fees, repairs and maintenance, insurance and, subject to the finance-cost restriction, mortgage interest relief at the basic rate. Pension contributions and Gift Aid can also reduce a higher earner’s liability. Keep all records for at least five years after the 31 January filing deadline.
Penalties for filing or paying late
HMRC penalties are automatic and escalate quickly. A return filed even one day late after the online deadline incurs a £100 fixed penalty — regardless of whether any tax is owed. After three months, daily £10 penalties can accrue up to £900, with further fixed or percentage-based penalties at six and twelve months. Late payment adds interest plus surcharges at 30 days, six months and twelve months. The simplest way to avoid all of this is to file early and pay on time; if you genuinely cannot pay, contacting HMRC about a Time to Pay arrangement is far better than ignoring the deadline.
How Accuprime helps
As your authorised agent, we take the whole return off your plate. We register you with HMRC if needed, gather and reconcile your figures, prepare the return, check every relief and allowance, and file it well before the deadline. We tell you exactly what to pay and when, including any payments on account, and we keep you ready for upcoming changes under Making Tax Digital for Income Tax. If you run a company, we can pair this with corporation tax and director payroll, and if you are weighing up incorporation we can advise on limited company setup.
Based in Reigate, we act for clients throughout Surrey, London and the rest of the UK. Explore our full range of tax services, read our guide to Making Tax Digital for small businesses, or learn more about working with a local accountant in Reigate. You can also review HMRC’s own guidance on Self Assessment tax returns for the latest official rules.
Frequently Asked Questions
Who needs to file a Self Assessment tax return? ▼
You generally need to file if you are self-employed earning over £1,000, a partner in a partnership, a landlord with rental income, a higher earner (for example over £150,000), receive untaxed income from savings, dividends or abroad, or are liable for the High Income Child Benefit Charge. Company directors with untaxed income often need one too. Check GOV.UK if unsure.
When is the Self Assessment deadline? ▼
Paper returns are due by 31 October following the end of the tax year (which runs 6 April to 5 April). Online returns and any tax owed are due by 31 January. If you make payments on account, the second instalment is due by 31 July. Register with HMRC by 5 October if you are filing for the first time.
What are payments on account? ▼
Payments on account are advance payments towards your next tax bill, due if your Self Assessment liability is more than £1,000 and less than 80% is collected at source. You pay two instalments, each 50% of the previous year’s bill, on 31 January and 31 July. A balancing payment then settles any difference the following January.
What expenses can I claim on Self Assessment? ▼
Self-employed people can claim allowable business expenses such as office costs, travel, stock, professional fees, insurance and a proportion of home-working costs. Landlords can claim agent fees, repairs, insurance and (with restrictions) finance costs. Expenses must be wholly and exclusively for the business. Keep records for at least five years after the 31 January deadline.
What are the penalties for filing late? ▼
Missing the online deadline triggers an automatic £100 penalty even if no tax is due. After three months, daily penalties of £10 can apply (up to £900), with further penalties at six and twelve months. Late payment also attracts interest plus surcharges. Filing and paying on time, or contacting HMRC early, avoids these costs.
Can an accountant complete my Self Assessment for me? ▼
Yes. As your authorised agent we can register you, gather your figures, prepare and file the return, check every relief and allowance, and tell you exactly what to pay and when. This reduces errors, removes the stress of HMRC deadlines, and often saves more in tax than the fee costs. We act for clients across Surrey, London and the UK.
Get help with your Self Assessment
Free initial consultation. We register you, prepare your return and file it on time so you avoid HMRC penalties.