Self-Assessment, why do I have to make a return and when do I have to pay?

Paula • 25 July 2024

Self-assessment is the system used by HM Revenue and Customs (HMRC) to collect Income Tax from individuals. Tax is usually deducted automatically from wages, pensions, and savings, but people who run businesses, rent property or have multiple income streams must report it in a self-assessment tax return.


Who Needs to File a Self-Assessment Tax Return?


You must send a tax return if, in the last tax year (6th April to 5th April), you were:


  • Self-employed as a ‘sole trader’ and earned more than £1,000 (before deducting anything you can claim tax relief on).
  • A partner in a business partnership.
  • Receiving income from renting out property.
  • Earning tips and commission.
  • Receiving income from savings, investments, and dividends.
  • Having a total income over £100,000.
  • Claiming Child Benefit and your income (or your partner’s) was over £50,000.
  • Make a profit (capital gain) on the sale of any assets, such as a house you don’t live in.


Key Deadlines


  • Registering for Self-Assessment: by 5th October following the end of the tax year you need to file for.
  • Paper Tax Returns: by the 31st October.
  • Online Tax Returns: by 31st January following the end of the tax year.
  • Paying Tax Owed: by 31st January following the end of the tax year.
  • Payments on Accounts: by the 31st July the year following the end of the tax year.


If you’ve never filed a tax return before, you will need to register for Self-Assessment online. This involves setting up an account with HMRC.  After registering you will receive your 10 digit Unique Taxpayer Reference (UTR).


Completing and submitting the tax return can be a complex task.  You will need details of business income and expenses, other income, pensions and dividends and other tax-deductible items such as allowances and donations. Using a professional will ensure that everything is reported correctly and that you declare and pay the correct amount of tax.  Accounting professionals will have use of bespoke software through which they can file directly to HMRC saving you valuable time while also giving you peace of mind.

Tax due needs to be paid by the 31st January the following and if a payment on account is due this will need to be paid by the 31st July.


So what are Payments on Account?


Payments on Account are advance payments towards your tax bill. They are made twice a year by taxpayers who file a self-assessment tax return, with the goal of spreading the cost of the tax liability more evenly across the year.


Who Needs to Make Payments on Account?

You must make Payments on Account if your last self-assessment tax bill was more than £1,000.  You do not have to make Payments on Account if more than 80% of your tax was collected at source (e.g., through PAYE).


How Payments on Account Are Calculated?

Each payment is half of your previous year's actual tax bill. For example, if your tax bill for the 2022-23 tax year was £4,000, you will make two Payments on Account of £2,000 each for the 2023-24 tax year.


When are Payments Due?

The first payment is due by 31st January during the tax year which it applies to.  It is paid at the same time as the tax that is due from the previous year.  The second payment is due by 31st July following the end of the tax year on the 5th April.


The Balancing Payment

If your actual tax bill for the current year is higher than the Payments on Account made, you will need to pay the additional amount by 31st January following the end of the tax year.  If your actual tax bill is lower, you will receive a refund or you can offset it against future tax bills.


Adjusting Payments on Account

If you expect your income to decrease and believe your tax bill will be lower than the previous year, you can request to reduce your Payments on Account.  However, if you do reduce the payment and the amount due is more than you paid you will be liable for interest payments on the unpaid amount.  It is always best to complete and file the return before the end of July to be certain of the amount that is due.


Tips for Managing Self-Assessment


  • Keep Accurate Records: Maintain detailed records of all your income and expenses. 
  • Use Software: Consider using accounting software to help manage your finances and make filing easier.
  • Plan for Payments: Set aside money throughout the year to cover your tax bill to avoid a financial crunch.  And remember that if you need to make payments on account you will need to save more than just the current tax bill.
  • Seek Professional Help: By engaging the services of an accounting professional you will have the assurance that your tax return has been completed correctly and all relevant information has been used.  Even with simple returns it is easy to make errors which could lead to costly penalties and fines… and even worse, paying more tax than you should.


M:Power Accounting are specialists in self-assessment tax and can lift the burden of compliance from you.  We will ensure that your tax return is correct and filed on time.  The earlier a return is filed the more accurate any reduction of payments on account will be.  We don’t want you to pay a penny more to the tax man than you should.


Please contact us to see how much we can help you. Let us deal with your tax return so that you can spend more time enjoying the things you like to do. 




Image credit: Photo by Nataliya Vaitkevich

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by Paula Veysey-Smith 9 July 2025
With many tax payers facing yet another payment to the HMRC on the 31st July let’s answer some frequently asked questions about the Payments on Account System. When was this system first introduced? The Payments on Account system was introduced in the 1996–97 tax year , as part of the Self-Assessment overhaul. Before then, HMRC had a fragmented and less predictable system for collecting income tax from self-employed individuals and others outside the PAYE system. It was introduced to ensure that taxpayers pay tax closer to when they earn their income , rather than facing a large lump sum payment long after the end of the tax year. Why did HMRC introduce Payments on Account? There are three key reasons why HMRC introduced this system: Cash flow for HMRC : This undoubtably is a driving reason for Payments on Account as it spreads the inflow of tax revenue more evenly throughout the year rather than relying on one big payment annually after a tax demand was sent to the tax payer. Encourages prompt payment : Tax is collected in advance (based on the prior year’s bill), reducing the risk of default or late payments. Helps tax-payers budget : Although first going into the Payment on Account system is painful as your tax bill, and half of it again, need to be paid on 31st January. Once in though, it does avoid the shock of a large single tax bill by splitting the liability into two smaller payments. So how does the Payments on Account system work? Who Needs to Make Payments on Account? You’ll need to make payments on account if your tax bill is more than £1,000 and less than 80% of your tax is collected at source (e.g., via PAYE). When Are Payments on Account Due? There are two payments each year: 31 January – First payment on account for the current tax year 31 July – Second payment on account for the current tax year Each is 50% of your previous year’s tax bill (excluding Class 2 NICs and student loan repayments). Example: Let’s say your tax bill for the 2023/24 tax year is £6,000 . On 31 January 2025 : You pay the £6,000 balance for 2023/24 Plus a £3,000 payment on account for 2024/25 (50% of £6,000) On 31 July 2025 : You pay another £3,000 as the second payment on account for 2024/25 So by July 2025, you've prepaid £6,000 towards your 2024/25 tax bill. What Happens When You File Your Next Tax Return? When you submit your 2024/25 return: If the actual tax bill is £7,000 , you’ve already paid £6,000 , so you owe £1,000 by 31 January 2026. If it’s only £5,000 , you’ve overpaid and can get a £1,000 refund or offset it against future payments. If the bill is £7,000 your tax payment will be: on 31st January 26 £1,000 balance on the 2024/25 return bill AND half of the £7,000 (£3 500) balancing payment so £4,500 in total. £3,500 balancing payment on the 31st July 26. Can You Reduce Payments on Account? Yes you can. If you expect your income to fall, you can apply to reduce them through your HMRC online account or on the paper form SA303. But if you reduce them too much, HMRC may charge interest on the underpaid amount. Will Making Tax Digital for Self-assessment change the Payments on Account System? The short answer is No! The longer answer is watch this space!! Many of us professionals believe that with quarterly reporting, quarterly paying will soon follow! For more information on Making Tax Digital for Self-assessment please see our article at: https://www.mpoweraccounting.co.uk/how-will-i-be-affected-by-making-tax-digital-for-income-tax-mtd-for-itsa The Payment on Account system often causes much confusion with self-assessment tax payers. At MPower Accounting we are used to helping our clients understand when payments need to be made and how they have been calculated. As an added service we will always send a payment reminder to clients early in July so they are not caught out. We are also delighted to work with clients who want to complete their self-assessment tax returns early to determine if they are able to reduce the July Payment on Account. Do contact us if you’d like help with Payments on Account and anything to do with your self-assessment
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