Switzerland’s 300 banks have enlisted an army of auditors, lawyers and in-house workers as they race to meet a Dec. 31 deadline on whether to seek U.S. amnesty for helping American clients evade taxes.

Banks in Switzerland, the largest cross-border financial center with $2.2 trillion of assets, are closely examining accounts before joining a disclosure program that’s the broadest assault in a five-year U.S. crackdown on offshore tax evasion.