Self-Assessment Tax Returns
Your income reported correctly, your tax calculated accurately, and your return filed on time.
Who needs to file a self-assessment tax return?
Self-assessment is how you report income to HMRC that isn’t already taxed through PAYE. You’ll need to file if you have:
- Self-employment income — freelancing, contracting, running your own business
- Rental income — from property you let out
- Foreign income — earnings from overseas sources
- Capital gains — profit from selling assets like property, shares, or cryptocurrency
- Dividends — if you’re a director taking income from your limited company
- High income — earning over £100,000, or liable for the High Income Child Benefit Charge
Can you do it yourself?
Yes — especially if you have a single, straightforward income stream. You can use HMRC’s online portal, though it’s not the most accessible interface. If you have multiple income streams, find numbers stressful, or want someone to check your figures, an accountant can save you time and worry.
What does a self-assessment tax return involve?
Self-assessment is the process of reporting all your taxable income for the year, calculating what you owe, and paying it. This includes:
- Gathering your records — income, expenses, bank statements, invoices
- Calculating your taxable income — after your allowable deductions
- Reporting figures to HMRC — via the online portal, software, or through an accountant
- Paying what you owe — by the deadline, and sometimes paying in advance of next year
What counts as income?
Most sources: self-employment, rental income, dividends, pensions, foreign income, and capital gains. Benefits like Universal Credit aren’t taxable. Access to Work grants are — if you receive them, talk to us about how to report them correctly.
The £1,000 trading allowance:
You can earn up to £1,000 from self-employment or casual income without reporting it. But if HMRC considers your activity a business, you may need to report it regardless of the amount.
When are the self-assessment deadlines?
Self Assessment Registration Deadline:
If you’re new to self-assessment, you must register with HMRC by 5 October following the end of the tax year.
Self Assessment Filing Deadlines:
- Paper returns: 31 October
- Online returns: 31 January
Self Assessment Payment Deadline:
Any tax owed is due by 31 January. If your bill is over a certain threshold, you may also need to make “payments on account” (advance payments towards next year’s tax).
What happens if you miss the deadline?
Late filing triggers an automatic £100 fine, even if you don’t actually owe HMRC any tax. After three months, these penalties increase. After six months, you’re looking at a minimum of £300, or 5% of the tax due, whichever is greater.
How does the self-assessment process work?
- You send us your records — bank statements, invoices, receipts, and details of all income sources
- We prepare your return — calculating your income, expenses, and tax liability
- We send you a draft for review — you check the figures before anything is submitted
- We file on your behalf — once you’ve approved the return
- We confirm what you owe — and when it needs to be paid
Why use an accountant for self-assessment?
Accurate tax returns for simple and complex income situations
Multiple income streams, capital gains calculations, and allowable expenses can get complicated. We make sure everything is reported correctly, even if your situation isn’t straightforward.
Review before submission with expert guidance
You review a draft of your return before it’s submitted to HMRC, so you can ask us questions if you’re not sure how something has been calculated. No need for anxiety about whether you’ve made a mistake.
Better for accessibility and focus
If you’re disabled, neurodivergent, or just find long forms overwhelming, we handle the process so you don’t have to. You can properly focus on running your business while we take care of your tax return.
Self-Assessment Tax Returns
- Preparation and filing of your annual tax return
- Draft review before submission
- Calculation of tax liability and payment dates
- Ongoing support and queries throughout the year
Your Self-Assessment Tax Returns with Watmore & Co
We prepare your return based on the records you provide, then present a draft for your approval before filing. Most of the process can happen via email — you don’t need to attend meetings unless you want to.
If you have cryptocurrency investments, we can help. Not many accountants handle crypto, but we do — as long as you can verify the source of your funds (this is a legal requirement for anti-money laundering compliance).
A note on Making Tax Digital:
From April 2026, Making Tax Digital for Income Tax will start replacing traditional self-assessment for some self-employed people and landlords. If your combined income from self-employment and property exceeds £50,000, you’ll need to keep digital records and file quarterly updates. We can help you prepare for this change.
Other Common Questions
What's the difference between current annual self-assessments and the upcoming Making Tax Digital changes?
Self-assessment is the current system where you file one annual return by 31 January.
Making Tax Digital (MTD) for Income Tax Self Assessment (ITSA) is being phased in from April 2026 — it requires quarterly digital updates as well as the annual return.
MTD applies to those with self-employment or property turnover (income before tax), which is over:
- £50,000 (from April 2026)
- £30,000 (from April 2027)
- £20,000 (from April 2028)
Do I need to report cryptocurrency?
Yes. Crypto profits are typically treated as capital gains — you report them when you sell, swap, or spend crypto at a profit. If you’re trading frequently (day trading), it may be treated as income instead. We can advise on how your situation should be reported.
Is selling things online taxable?
Selling personal items (clearing out your wardrobe, for example) is generally hobby income and not taxable. But if HMRC considers your activity a business — regular selling, buying to resell, treating it as a side hustle — you may need to report it even if you earn under £1,000.
What about Access to Work grants?
Access to Work grants are reportable income if any amount you receive goes unused. You shouldn’t claim associated Access to Work expenses if you’re not also reporting your grant income, because this would mean you’re artificially reducing your profit, which could be considered tax evasion.
Can I pay my tax bill through my tax code?
If you’re employed and owe less than £3,000, you can ask HMRC to collect the tax through your PAYE code the following year. However, to do this, you must file your return by 30 December (not the usual 31 January). We can advise if this option suits your situation.
What records do I need to keep?
Bank statements, invoices, receipts for business expenses, records of any assets you’ve sold, and details of all income sources. If you’re self-employed or a landlord, you’ll need to keep records for at least five years after the 31 January deadline.
What are payments on account?
If your Self Assessment tax bill is over £1,000 (and less than 80% of your tax is collected through PAYE), HMRC will ask you to make “payments on account”. These are advance payments towards next year’s tax bill.
Here’s how it works: HMRC takes your previous year’s tax bill and splits it in half. You pay the first half by 31 January (at the same time as your balancing payment for the previous year) and the second half by 31 July.
This can come as a surprise the first time it happens — you might expect to pay one year’s tax, then suddenly owe up to 1.5 times that amount in January. It’s worth knowing about early so you can budget for it.
If your actual tax bill ends up being lower than the payments on account, you’ll get a refund. If it’s higher, you’ll pay the difference as a “balancing payment.” You can also apply to reduce your payments on account if you’re confident your income will be lower — but be careful, as underestimating can lead to interest charges.
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