Karthik was spotted in the dressing room of the Tribango Knight Riders in the opening match of the Caribbean Premier League (CPL) against St Kitts and Nevis Patriots on Thursday, ESPN Cricinfo reported.
The BCCI contracts do not allow any player to participate or be present at any other sporting activity without taking permission from the board.
During the CPL match, Karthik was seen seated next to former Kiwi skipper Brendon McCullum.
It is important to note that the owners of Karthik's Indian Premier League (IPL) franchise, Kolkata Knight Riders also own Trinbago Knight Riders in the CPL.
The player has been issued a notice and he has been given a week to respond to the charges.
Karthik last played an international match in the recently concluded World Cup. He played the semi-final game against New Zealand, which the team eventually lost.
After that, he was dropped from the team squad for the limited-over series leg against West Indies.
Recently, he was appointed as the captain of Tamil Nadu for the upcoming Vijay Hazare trophy.