It reported a loss of 983 million Swiss francs (€851 million euros $1.05 billion) in 2017, down from 2.7 billion Swiss francs the previous year.
The second-largest Swiss bank had warned in December that the US tax reforms would hit its fourth-quarter results.
In the last four months of the year, net losses were 2.1 billion Swiss francs, slightly less than forecast by analysts interviewed by Swiss agency AWP who had predicted a figure of around 2.2 billion.
Over the year as a whole, the bank exceeded its cost reduction target, bringing its operating cost base down to 17.7 billion Swiss francs.
It was the second year of a three-year reorganisation of the bank's activities to focus on wealth management over merchant banking.
The repositioning aims to reduce the volatility of the group's results, as merchant banking activities are more sensitive to market turmoil than asset management.
"2017 was a crucial year of delivery in our three-year restructuring plan, after 2016, which was a year of deep and radical reorganisation," chief executive Tidjane Thiam was quoted as saying in a company statement.
"It was key for us to demonstrate that our new structure is effective and that the strategy formulated in 2015 is working."