April 30, 2026
General
Amanda Perrotton

Discovering a tax error is never ideal, but what happensnext can have a significant impact on the outcome. Acting quickly, takingadvice early, and addressing the issue head-on can reduce both the financialcost and the likelihood of a wider HMRC investigation.
The UK tax system is designed to encourage transparency. Inpractice, this means that businesses who come forward voluntarily are oftentreated far more favourably than those where HMRC uncovers the issue itself. Aproactive disclosure can limit disruption, reduce management time spent dealingwith enquiries, and in some cases prevent a more extensive investigationaltogether.
Penalties for tax errors are largely driven by behaviour.Where reasonable care has been taken, there may be no penalty at all. At theother end of the spectrum, deliberate concealment can result in penalties of upto 100% of the tax due, and even higher in certain offshore cases.
However, the key point is this: penalties can often besignificantly reduced — sometimes to nil — where a taxpayer makes a full andunprompted disclosure. In other words, telling HMRC before they come to you canmaterially change the outcome.
This is particularly important where an issue is ongoing.For example, a business that realises it should have been VAT registered cannotsimply ignore the position going forward. Taking steps to correct it willinevitably bring the historic position into view, and handling that disclosureproperly becomes critical.
No two situations are the same, but a structured approach isessential. This usually involves confirming the position through a detailedreview, making an initial disclosure to HMRC to preserve the “unprompted”status, and then carrying out a full analysis to quantify any liability.
A well-prepared disclosure does more than just calculate thetax due. It explains how the error arose, sets out the behaviour at the time,and demonstrates that the issue has been properly investigated. This level ofclarity can make a real difference when HMRC considers penalties.
Where appropriate, making a payment on account early canalso help limit interest costs, which can otherwise build quickly.
A clear and comprehensive disclosure can significantlyreduce the likelihood of HMRC opening a wider, more intrusive enquiry. Somefollow-up questions are to be expected, but the quality and transparency ofresponses will often determine how quickly the matter is resolved.
Handled properly, a voluntary disclosure can notonly reduce penalties but also bring certainty and closure far more efficientlythan allowing matters to escalate.

