BRUSSELS, June 3 (Reuters) - EU antitrust regulators are

asking retailers and payments companies whether a standardized

summary of fees by Visa and Mastercard ( MA ) and more

transparency on the charges would address their concerns,

according to documents seen by Reuters.

The latest questionnaires sent on Tuesday, which came nearly

two months after the last batch, suggest that EU regulators have

escalated their preliminary investigation into Visa and

Mastercard ( MA ).

The two companies, which charge scheme fees for services

related to participation in their card system and process about

two-thirds of card payments in the euro zone, have long faced

complaints from merchants and payments companies.

The new questionnaires focus primarily on a simpler and more

transparent fee structure and how Visa and Mastercard ( MA ) should

handle fines levied on retailers and payments companies.

Visa and Mastercard ( MA ) did not immediately respond to requests

for comment.

Respondents were asked whether a standardized summary of

fees categorized by type by Mastercard ( MA ) and Visa, including

descriptions and services covered, and drafted in plain and

intelligible language would be a suitable solution.

The 11-page questionnaires asked if changes to contracts

including terms and conditions, services and fees should be

based on objective, transparent, general and non-discriminatory

criteria.

Regulators wanted to know if a requirement for card schemes

to invoice fines separately would help retailers and payments

companies to identify the reason for the levies and to challenge

them when appropriate as well as the process for contesting

them.

The deadline for replies is June 18.