The US and Switzerland have signed a double tax agreement (DTA) held in limbo for the past ten years that will allow US authorities to check bank details going back ten years.

The ratification of the tax treaty – which had been blocked by US Senator Paul Rand since September 2009 – means that requests for financial accounts must relate to cases which have occurred since the date of signature of the protocol of amendment, i.e. 23 September 2009. At the same time, under the FATCA Agreement, group requests are admissible for cases from 30 June 2014.

The Swiss government said that the core element of this revision is th...