“In most of the conversations that we have had recently, someone has brought up the hassle of supplying personal-identification data,” said Lalone, a partner at the law firm. “And some countries have rules that make it harder to pass on this information. South Korea is very, very strict.”

There’s also the question of what should be done with the rule breakers. MiFID technically requires traders be barred until they cough up the information, but U.K.-based venues have been double checking with the Financial Conduct Authority, which has yet to respond.

“Fines are one lever,” said David Howson, chief operating officer at Cboe Europe. “We might disallow connections. The final measure is to stop them submitting orders to the order book. It’s one of the main pain points and one of the main risk areas for us with MiFID II.”

Meanwhile, the bond venues are waging a lobbying campaign to get the rules changed. The trade body Electronic Debt Markets Association -- representing Tradeweb, MarketAxess Holdings Inc., NEX and MTS Markets, the debt-trading division of LSE -- sent a letter to the European Securities and Markets Authority last month warning of potentially dire consequences from the data requirement.

Haven’t Succeeded

“Fixed-income venues spent several years trying to raise this issue,” said David Bullen, the secretary general of EDMA Europe. “We tried to get this done through the right channels and it goes without saying that we haven’t succeeded yet.”

Bloomberg LP, the parent of Bloomberg News, operates a bond-trading venue and sells products for MiFID II compliance.

The personal-data rules “cannot be amended or altered through legal instruments available to ESMA” because they were included in the original MiFID text that was signed off by Europe’s leaders and the trading bloc’s parliament, ESMA said in an email.

“There’s a real chance people will decide not to trade” on our EU platform, said Ben Pott, group head of government affairs at NEX Group Plc, an operator of debt and currency markets. “We do not want to get into arguments. The moment you have a non-MiFID firm and you are asking for their personal data, that’s a difficult conversation.”

Some Winners