They say they are owed the money by the Northern Ireland Court Service for work on cases dating back more than four years.
The Bar Council, which represents barristers, is negotiating with the Court Service in an attempt to reach a settlement.
However, the barristers have warned they could start sending back briefing papers from solicitors as soon as this Friday.
The barristers are also seeking an increase in the fees for legal aid cases in magistrates' courts, which have not been changed since 1993.
