ESS software is software which is designed to hide certain sales from accounting records and hence understate income on which tax is paid to HMRC.
The software is typically used by retail outlets and allows a certain proportion of sales , even though they are keyed into the electronic tills, to be omitted from the takings figures. Where the sales are paid by credit card, the takings will typically be paid into an offshore bank account.
HMRC have identified certain individuals who have designed and sold this software. HMRC have also identified some businesses which have purchased the software. Consequently HMRC are in the process of commencing tax enquiries into those businesses, in order to establish the extent of the tax evasion and criminal activity.