Do I need to complete a self-assessment tax return if I have done a capital gains tax return?

Your personal circumstances will determine whether that is the end of the process or not. If you already complete a self-assessment tax return, then you will still need to do so, and will need to report the gain on the tax return. If you don’t already complete a self-assessment tax return, you won’t need to register for self-assessment and complete a return unless there is any other reason why you might need to do so.

If there is any additional capital gains tax (CGT) to pay, then this can be paid via self-assessment. 

How could I under- or over-pay CGT through the 60 day CGT return? 

You could under- or over-pay CGT because rates of capital gains tax are geared to your personal income tax rates. 

This means that what other income and gains you have in the tax year will determine how much of each tax band you have used up, once you have also used the personal allowance and the CGT annual exempt amount. 

Once actual income details for the year of sale are known, if your income was lower than expected or other reliefs become available to you, this can result in an overpayment of CGT on the property sale. 

What if I have overpaid CGT? 

If you realise you have overpaid CGT on the sale of your property, you can amend your 60 day return through your CGT on UK Property account online as long as: 

• the CGT was payable in the tax year 2024/25 or later (as of 2026/27) 
• you have not yet filed your self-assessment tax return for that year 

If you cannot amend your 60-day return in this way, you can print and send a return in the post – see the information here. 

HMRC guidance states that if you have overpaid CGT via your CGT on UK Property account, it will be automatically offset against other self-assessment tax liabilities when you file your tax return. If there is still an overpayment after this offset, you must call HMRC on 0300 200 3300 to arrange a repayment.  

How can TaxAssist Accountants help? 

TaxAssist Accountants are well versed in the process for 60-day CGT returns for UK residential property sales and can manage the entire process for you, including your self-assessment tax return if required. 

If you would like any advice or assistance in this area, please contact us on 0161 7140464 or use our simple online contact form to arrange a free initial consultation.

Last updated 30 Jul 2026 | First published 15 Oct 2021

Share

This article is intended to inform rather than advise and is based on legislation and practice at the time. Taxpayer’s circumstances do vary and if you feel that the information provided is beneficial it is important that you contact us before implementation. If you take, or do not take action as a result of reading this article, before receiving our written endorsement, we will accept no responsibility for any financial loss incurred.

---