7 ways to avoid making Self Assessment tax return mistakes

Whether in business or life, mistakes are inevitable. In some ways, they’re a good thing, because they offer us the opportunity to learn and improve. The challenge is to not let the same mistakes happen again,…

5 Minute Read

Last Updated: 23rd March 2023

Whether in business or life, mistakes are inevitable. In some ways, they’re a good thing, because they offer us the opportunity to learn and improve. The challenge is to not let the same mistakes happen again, of course, although that’s never a given.

Mistakes are much more likely when you lack knowledge and experience. And that’s as true of filling out and filing a Self Assessment tax return as anything else when you’re a sole trader, business partner or private residential landlord.

Self Assessment tax return mistakes

If we’re lucky, we make minor mistakes with no major consequences. Often, we can easily correct silly errors. But sometimes mistakes have bigger repercussions, and that can happen when you’re completing your Self Assessment tax return.

Failing to file your Self Assessment tax return before the filing deadline will result in a late-filing penalty unless you have a justifiable reason. And if you leave out essential information/data in your Self Assessment tax return, your time can be severely disrupted if HMRC later contacts you for information and maybe decides to investigate. Moreover, if you enter incorrect figures, you can pay more tax than you owe. So, how can you prevent mistakes when doing your Self Assessment tax return?   

1. First improve your Self assessment tax return know-how

If you’ve not done any or many Self Assessment tax returns before, you’ll lack knowledge. But basic know-how can be gained from reliable online sources, including these pages and those on government/HMRC website GOV.UK. You can soon learn a lot and the trick is to focus on the things most relevant to your income or tax circumstances.

Need to know! HMRC publishes guidance notes on filling in the main Self Assessment tax return form (SA100) and supplementary tax return pages.

2. File your Self Assessment tax return early

It’s a busy life for many people, with plenty of tasks, demands and responsibilities to juggle. It’s a key reason why so many people miss the Self Assessment tax return online filing deadline each year (that and a dislike or fear of completing tax returns).

But you don’t have to leave it until the last few hours, days or weeks before the 31 January Self Assessment tax return online filing deadline. You can file your Self Assessment tax return on 6 April, when the new tax year begins. About 65,000 people do this each year. The sooner you do it, the sooner you can get it off your plate. And the more time you leave to complete your Self Assessment tax return, the less pressure you’ll feel, so you can relax and get it right.

Need to know! If you need to complete a tax return for the first time, you’ll first need to register for Self Assessment.

3. Don’t rush when completing your Self Assessment tax return

You also need to dedicate enough time to completing your Self Assessment tax return. Rushing increases the risk that you’ll miss something out or fail to enter the right information in the right place, so you underreport income or fail to claim allowances and reliefs to which you’re entitled.

Reportedly, the average person takes about three hours to complete their Self Assessment tax return. Set aside that time at least, in a place where you won’t be distracted. Turn off your phone and take your time; stay focused and methodically work your way through your Self Assessment tax return.

4. Make sure you have the information you need to hand

You won’t be able to complete your Self Assessment tax return if you don’t have the necessary figures to hand. That can mean your National Insurance number and UTR (Unique Taxpayer Reference) number, your financial records (ie accounts), invoices, receipts, details of all taxable income/earnings, records of costs, etc.

Top tip! Having tax returns for previous years to hand can help you to cross reference figures, so that you’re less likely to get them wildly wrong.

5. Claim all of your allowable expenses

Whether you’re a self-employed sole trader, ordinary business partnership member or private residential landlord, you may be able to claim a wide range of allowable expenses to help minimise your tax bill. To qualify as an allowable expense, something must be bought “wholly and exclusively” for business. Where there’s mixed business and personal use (eg mobile phone costs), you must reliably work out the proportionate cost for business use before claiming allowable expenses.

Read: 45 allowable expenses you can claim when you’re a sole trader or What expenses can landlords claim against tax?

6. Include details of all taxable income

You may not realise that some of your income must be reported via Self Assessment. That could include Child Benefit if you or your partner earns more than £50,000 a year, income earned overseas, pension income, share dividends, interest, earnings from casual part-time work, tips or commissions or Capital Gains Tax if you sell a property or other valuable asset.

Leaving out taxable income lowers your tax bill and there can be serious consequences for deliberately doing so. If you’ve filed your tax return but haven’t declared all of your taxable income, you can later amend your tax return and your bill will be recalculated, but getting it right the first time can prevent a lot of unnecessary hassle.

 7. Get your Self Assessment tax return checked by an expert

There really is no substitute for experience. And although you can save money by doing your own Self Assessment tax return, which is made all the more easier by using good software, paying a relatively low fee to have an expert look over it can provide additional peace of mind. A Self Assessment tax return expert can quickly point out errors and tell you about any allowances or reliefs that you should be claiming, which can help to lower your current and future tax bills.

GoSimpleTax is award-winning software that offers you an easier way to complete and file your Self Assessment tax return. And to ensure that your tax return is error-free and that you’re claiming all of your allowable expenses, why not get your Self Assessment tax return checked by one of our experts?

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Blog content is for information purposes and over time may become outdated, although we do strive to keep it current. It's written to help you understand your Tax's and is not to be relied upon as professional accounting, tax and legal advice due to differences in everyone's circumstances. For additional help please contact our support team or HMRC.

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