The United States' Internal Revenue Service (IRS) has extended its requests to a group of 40 Swiss banks to disclose full details of client accounts held by US citizens.

Switzerland's Federal Tax Administration on Monday (28 June) published a list of 40 banks, fiduciary firms and insurance companies, here.

The online broker Swissquote, headquartered on Lake Geneva, is the latest Swiss financial institution featuring on the list of the IRS, according to Swiss Info.

It is the fourth update of group administrative requests by the Internal Revenue Service (IRS) since last December under the Foreign Account Tax Compliance Act (FATCA).

The American clients concerned now have 20 days to submit their opinion on the intended transmission of their data to the IRS, before the Swiss authorities will issue a final decree, the Federal Tax Administration said.

The agreement between the US and Switzerland on cooperation to simplify the implementation of FATCA came into force in 2014.

Under the deal, Swiss financial institutions disclose account details directly to the US tax authorities with the consent of the US clients concerned.

Where US clients refuse to give their consent, Washington has to request this data through normal administrative assistance channels, according to the State Secretariat for International FinanceExternal link.