This is the first agreement of its kind and will boost HMRC's ability to obtain information from the US to help tackle tax evasion.
It will also help with implementing FATCA (Foreign Account Tax Compliance Act) and addresses legal barriers to financial institutions complying with FATCA.
The aim of FATCA is to combat tax evasion by US tax residents who are using foreign accounts.

The UK-US agreement will ensure withholding tax will not be imposed on income received by UK financial institutions or the payments they make and ensure the burden imposed on financial institutions is proportionate to the goal of combating tax evasion.
David Gauke, exchequer secretary to the Treasury, said: "This agreement demonstrates our commitment to working internationally to tackle tax evasion. It's the first of its kind and represents a significant step forward in the scope and nature of information exchange between governments.
"Furthermore, the changes we have achieved to FATCA implementation will provide significant benefits to UK financial institutions."
The agreement follows a Joint Statement in July 2012 by the governments of France, Germany, Italy, Spain, UK and US on the implementation of FATCA.