For disposals of assets other than residential property or carried interest made on or after 30 October 2024, the Capital Gains Tax (CGT) rates have increased: 

  • From 10% to 18% for basic rate taxpayers 

  • From 20% to 24% for higher rate taxpayers 

 

Software Limitation and Adjustment Requirement 
HMRC has confirmed that their systems—and by extension, third-party software—do not have the capability to apply split Capital Gains Tax rates for disposals made before and after 30 October 2024. Instead, all gains are calculated using the older rates (10% and 20%), regardless of the disposal date. 

To address this, HMRC has instructed software providers to post the difference in tax due under the new rates as an adjustment in box CGT51 on the Self-Assessment return. 

Capium’s Process During this Transition 
Capium now automatically displays a CGT information page whenever users attempt to post gains as shown in the screenshot below: 

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Recording gains before and after the budget.  

The budget gains effects all capital gains besides residential properties. Every section where you can disclose gains is followed up with another section where you can post gains after the budget.  

As user fills both these sections, the software will automatically calculate the higher rate tax on the gain and post it within the CGT box 51. This also reflects as an adjustment on the SA302Computation.  
 
Please see the steps and examples below: 

 

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Once the gain before 30 October 2024 and the gain after the 30 October 2024 are added the system will automatically do the calculation of the difference in tax due and post an adjustment in the CGT box 51 as shown below.  

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You can also verify the same in the SA302 calculation as shown below. 

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Reference 

For further information, please refer to HMRC's official guidance: 
Work out your Capital Gains Tax adjustment – GOV.UK