Citibank in the US has been forced to apologise after mistakenly printing the social security numbers of 600,000 customers on the outside of envelopes containing their year-end tax statements.
The letters were sent via the US Postal Service in January, and had the numbers printed on the envelopes' lower edges.
In letters sent to affected customers, Citibank said the error was down to a "processing error", and promised it would not happen again.
"We believe there is little or no risk to you," said Citibank in the letter. However, the bank is offering affected customers a free 180-day credit monitoring service, to ensure no fraudulent activity results from exposing their personal information.



