NTB said its June quarter financials will be published as early as possible in July.
"The Bank has discovered a breach of procedure in its dealing room leading to an exchange loss," NTB said in a stock exchange filing.
"The loss resulting from the above breach does not adversely affect any of the liquidity and capital adequacy ratios, which will continue to remain well above the statutory requirements.
"The Bank is on track to meet this year's revenue and profit forecasts."
The bank did not disclose the volume of losses, or the period in which they were incurred.
Analysts say the bank is in line to make substantial profits on its government bond portfolio.
The bank has been active in foreign exchange operations, selling cross trading forex accounts to clients.