EU Tax Streamlining Runs Up Against Nations’ Money, Data Concern

The EU’s push to simplify its tax code through a bill due this summer risks clashing with individual countries’ priorities and dampening their enthusiasm for the effort, which will need unanimous support.

Some countries fear the bill that the European Commission promises as the “biggest review of European tax legislation ever” may result in their losing revenue or valuable information about companies’ tax arrangements, or both, according to people familiar with the matter.

Businesses and tax professionals warn that if nations block the measure, or water it down, the EU will be stuck where it is now: with ...