HMRC tax calculator errors are placing self-assessment taxpayers at risk as the 31 January deadline approaches. More than five million individuals have yet to submit returns, with many relying on automated tools to calculate liabilities. However, HMRC’s calculator does not fully reflect recent capital gains tax changes introduced in the 2024 Budget, increasing the risk of underpaid tax.

Experts warn that taxpayers reporting disposals may unknowingly submit incorrect figures. While HMRC states that sufficient tools exist to calculate liabilities accurately, confusion remains around applying revised CGT rates and exemptions. Errors can result in interest, penalties, and follow-up enquiries, even where mistakes are unintentional. This highlights the importance of reviewing figures carefully rather than relying solely on online calculators.

• HMRC tax calculator errors risk incorrect returns
• CGT rates changed after the 2024 Budget
• Over five million returns still outstanding
• Errors may trigger penalties and interest
• Professional checks reduce HMRC exposure.

How Holland & Co can help:

Holland & Co helps clients avoid penalties caused by HMRC tax calculator errors by reviewing self-assessment returns before submission. We offer a fixed-fee tax position review from £200 plus VAT to check capital gains calculations, income figures, and overall compliance. We can also help clients improve record-keeping, submit information faster using KashFlow, and carry out a full Financial Health Review to identify wider tax-saving opportunities across business structure, pensions, and investments. This proactive approach reduces risk, improves accuracy, and prevents avoidable HMRC disputes.