The lower house agreed to back the plan – which clarifies how Switzerland would hand over data on Americans suspected of dodging taxes at home – by 110 votes to 56.
Switzerland’s upper house passed the plan in December.
The proposal will allow Switzerland to hand over data on suspected tax evaders, even if US tax authorities can only identify alleged offenders by suspicious patterns of behaviour, rather than by name or bank account.
It seeks to backstop an expected deal over US probes into 11 banks including Credit Suisse and Julius Baer that is likely to comprise a data handover and fine payment.
The move represented a weakening of Switzerland’s secrecy laws, which have underpinned its finance industry on which the economy relies heavily.
But the Swiss authorities have agreed to compromise after the US indicted Wegelin, a small private bank, for allegedly assisting Americans to avoid $1.2bn of taxes.