Currently VAT regimes and other tax rates vary from 15% to 25% across the various member states, despite efforts made by the European Commission dating back more than 30 years.
But a third of company executives polled by US delivery company UPS said tax harmonistion would be the most significant improvement to be made across the region.
Setting a uniform tax rate would allow companies to charge the same price for their goods across the region, executives claimed.
However, the Confederation of British Industy continued its opposition to harmonisation, saying the UK had the lowest tax rate in the EU, and changes to this would erode its competitive position.
The UK government is also opposed to EU tax harmonisation.
Three tax advisers have been arrested as part of a HMRC investigation into a suspected £132m tax fraud.
HMRC intends to extend the date for withdrawal of transitional relief on investment growth from 30 November 2016 to 31 March 2017
Public opinion is split over whether Brexit will harm or improve the UK accountancy sector
What questions should the profession be asking now the UK has decided to leave the EU?