The European Union's head office estimates that the cost of fully restoring border controls between EU member states would be as high as 18 billion euros ($20 billion) a year.
As temporary controls between several member states are reimposed to deal with the migrant crisis, the fear of the full collapse of the borderless Schengen zone through most of the EU has increased over the past month.
The European Commission said Friday that the cost could amount to 0.13 percent of Gross Domestic Product. It estimated that cost for road transport alone could go as high as 7.5 billion euros ($8.2 billion) annually, hitting countries with major exports especially hard.
In a planning document on how to fully restore the Schengen zone by December at the latest, the Commission said that beyond trade, the reimposition of borders "would also risk putting in jeopardy the judicial and police cooperation."