The US Department of Justice (DoJ) has reached a resolution with Migros Bank and Graubündner Kantonalbank over the tax evasion cases under the department’s Swiss Bank Program.

Under the deal, the two Swiss banks have agreed to pay a combined $18m in penalties to the US.

Migros will pay $15.037m and Graubündner will pay $3.6m in penalties to the US to avoid prosecution over allegations accusing them of helping Americans evade taxes.

As per the terms of the non-prosecution agreements, the banks have agreed to cooperate in any related criminal or civil proceedings and demonstrate implementation of controls to prevent misconduct.

The DoJ said that Migros maintained and serviced 898 US related accounts with an aggregate value of $273m since 1 August 2008.

Migros Bank accepted referrals of US persons as new clients from an external asset manager based in Switzerland, which brought a total of 165 US related accounts to Migros from 2001 until 2005.

Graubündner maintained 364 US related accounts with an aggregate maximum balance of $105.5m.

The bank offered banking services including code word or numbered accounts and helped US clients in executing forms that directed Graubündner not to disclose their names to the IRS.

US Justice Department tax division acting assistant attorney general Caroline Ciraolo said: "With each agreement reached under the Swiss Bank Program, and each U.S. accountholder who initiates and completes a voluntary disclosure to the Internal Revenue Service, we move a step closer to eliminating secret undisclosed accounts."

IRS large business & international division acting deputy commissioner international David Horton said: "This settlement aids our efforts to make sure U.S. taxpayers report their foreign accounts and pay taxes on the income earned on those accounts. Working with DOJ, we continue to make progress fighting offshore tax evasion and those who aid such illegal activity."