The Swiss government has said the US Internal Revenue Service has formally lodged a request to its Swiss counterpart for data from UBS, beginning an administrative process aimed at getting information on as many as 4,450 clients of the Swiss bank, media reports said.

The request follows August’s settlement between the IRS and UBS, under which the Swiss banking and wealth management firm will transfer the client account details to US authorities.

Switzerland has set up a task force to work through the data, which represents an administrative task of record proportions for the country. Clients who find their data set for handover to the US authorities have the right of legal appeal in Switzerland against the transfer.

The project group is made up of roughly 40 legal and tax experts from the Swiss tax authority and up to 30 experts from an undisclosed audit company. The group is led by Hans-Joerg Muellhaupt, a lawyer and former judge who was hired by the Swiss tax office last year as an expert to help evaluate the initial the US' request for client data.