Can I Do My Own Self Assessment Tax Return?

If you are staring at a deadline, a pile of receipts and an HMRC login you have not used in months, the question is usually the same: can I do my own self assessment tax return? The short answer is yes, many people can. The better answer is that it depends on how simple your tax affairs are, how confident you feel with figures, and how much risk you are willing to carry if something is missed.

For some sole traders, landlords and subcontractors, filing your own return is perfectly manageable. For others, it turns into a false economy - especially when allowable expenses are overlooked, records are patchy, or income comes from more than one source. The key is knowing where you sit before you press submit.

Can I do my own self assessment tax return if I am self-employed?

If you are a sole trader with one clear income stream, decent records and straightforward expenses, you can often complete your own return online without too much trouble. That might apply if you are a cab driver keeping proper mileage and running costs, a subcontractor with CIS deductions clearly shown, or a landlord with a single rental property and well-organised paperwork.

HMRC's online system is designed for taxpayers to use themselves. It guides you through the sections, asks about your income and expenses, and works out the tax due based on what you enter. In simple cases, that can be enough.

Where people get caught out is not usually the form itself. It is the judgement behind the numbers. Knowing whether an expense is allowable, whether you should claim the trading allowance, how to treat use of home, what to do with a van or car, or how CIS deductions affect the final position is where mistakes tend to happen.

So yes, you can do it yourself. The real question is whether you can do it confidently and correctly.

When doing it yourself makes sense

DIY tends to work best when your records are tidy and your tax position is uncomplicated. If you have one trade, all your invoices or income records are accounted for, and your expenses are ordinary and easy to identify, the process is more administrative than technical.

It can also make sense if you are comfortable reading HMRC guidance and checking points carefully before filing. Some people are naturally methodical. They keep business and personal spending separate, save receipts as they go, and reconcile their figures regularly. For them, self assessment is often a manageable yearly task rather than a last-minute panic.

Cost is another reason people handle it themselves. If your affairs are very simple, paying for accountancy support may feel unnecessary. That is understandable, particularly in the early stages of self-employment when every pound counts.

Even then, it helps to be honest about the value of your time. Spending hours wrestling with tax rules in January may save a fee on paper, but not if it takes you away from earning.

When DIY can cost more than it saves

The biggest problem with a self-prepared tax return is not always paying too much tax. Sometimes it is paying too little and creating trouble with HMRC later. Sometimes it is both - missing legitimate expenses in one area while making an incorrect claim in another.

This is especially common where tax affairs are not as simple as they first appear. CIS workers may have tax deducted at source but still need the return prepared properly to claim any refund due. Landlords may need to separate repair costs from capital improvements. Directors can run into issues where salary, dividends and other income all need to be reported correctly.

There is also the question of timing. If you are filing close to the deadline and rushing through unfamiliar sections, the chance of errors goes up. A return submitted on time but filled with wrong figures is not much comfort.

For many working people, the appeal of using an accountant is not just compliance. It is peace of mind. You want to know the return is right, the tax position makes sense, and no obvious opportunities have been missed.

Common areas where people make mistakes

Expenses are one of the biggest stumbling blocks. It is easy to underclaim because you are being overcautious, or overclaim because you assume anything loosely connected to work counts. Travel, mobile phone costs, clothing, tools, home office costs and vehicle expenses all need care.

Record-keeping is another weak point. HMRC expects you to keep accurate records, and if your figures are based on estimates rather than evidence, that can become difficult to defend. This is a regular issue for busy tradespeople and drivers who are focused on the day job, not paperwork.

People also forget about other income. Interest, property income, side work, benefits in kind or capital gains may all affect the return. One missed section can change the tax calculation significantly.

Then there is payments on account. Many taxpayers are caught out not because the tax bill is wrong, but because they did not realise HMRC may ask for advance payments towards the next tax year as well. That can turn an expected bill into a much bigger one overnight.

Can I do my own self assessment tax return if I have CIS or rental income?

You can, but this is where caution matters.

If you work under CIS, your return needs to reflect the deductions already made by contractors. Get that right and you may be due a refund. Get it wrong and the numbers can quickly stop making sense. CIS tax returns are not impossible to do yourself, but they are less forgiving than a basic sole trader return with no deductions involved.

Rental income also looks simple until you get into the detail. Mortgage interest rules, replacement of domestic items, repair versus improvement costs, jointly owned property and periods when a property was empty can all affect what should be reported.

That does not mean you must use an accountant. It means you should be realistic. If your tax affairs involve special rules, the margin for error is smaller.

A practical way to decide

A useful test is to ask yourself three things.

First, do you understand all of your income sources and how they should be reported? Second, do you have complete records to support the figures? Third, would you know if you had missed a claim or entered something in the wrong place?

If the answer to any of those is no, getting advice is sensible. That does not always mean handing everything over forever. Some people benefit from help with their first return and then feel more confident later. Others prefer ongoing support because their time is better spent running the business.

A good accountant should not make things feel more complicated. They should simplify the process, explain what matters in plain English and help you avoid expensive guesswork. That is particularly valuable for self-employed people who are already juggling work, cash flow and admin.

If you do file your own return, do it properly

If you decide to go ahead yourself, do not leave it to the final week of January. Start early enough to gather records, check bank statements, review invoices and make sure your expenses are backed up. Keep business and personal costs separate where you can. Recheck your figures before submission, especially if you have CIS deductions, rental income or anything outside your main trade.

It is also worth looking beyond the tax bill itself. A well-prepared return should give you a clearer picture of how your business is performing. If your records are poor, the tax return often exposes a bigger issue in how the business is being run day to day.

That is one reason many clients come to firms like Short and Sons Accountants Ltd after trying to do it alone. The problem is rarely a lack of effort. More often, they are busy people who want the numbers sorted properly so they can get on with earning.

The right answer is the one that keeps you accurate

So, can I do my own self assessment tax return? Yes, absolutely - if your affairs are straightforward, your records are in order and you are comfortable taking responsibility for the final figures. But doing it yourself is only the right choice if it leaves you accurate, compliant and clear on what you owe.

If there is uncertainty, that is usually the point to get support. Tax should not feel like a guessing game, especially when one mistake can cost more than the fee you were trying to avoid. The best route is the one that lets you sleep at night and keep your focus where it belongs - on your work, your business and the next job ahead.