UBS estimates a negative impact of $US13 billion from fair value adjustments of the combined group's assets and liabilities. UBS also sees $US4 billion in potential litigation and regulatory costs stemming from outflows, the bank said.
UBS, however, also estimated it would book a one-off gain stemming from the so-called "negative goodwill" of $US34.8 billion by buying Credit Suisse for a fraction of its book value.
The financial cushion will help absorb potential losses and could result in a boost to the lender's second-quarter profit if UBS closes the transaction next month as planned.
UBS said the estimates were preliminary and the numbers could change materially later on.
The bank also said it might book restructuring provisions after that, but offered no numbers.
Analysts at Jefferies had estimated restructuring costs, litigation provisions and the planned winding down of the non-core unit could total $US28 billion.
UBS agreed in March to buy Credit Suisse for three billion Swiss francs ($US3.4 billion) in stock and to assume up to five billion francs in losses that would stem from winding down part of the business, in a shotgun merger engineered by Swiss authorities over a weekend amid a global banking turmoil.
The deal, the first rescue of a global bank since the 2008 financial crisis, will create a wealth manager with more than $US5 trillion in invested assets and over 120,000 employees globally.
The Swiss state is backing the deal with up to 250 billion Swiss francs in public funds.
Switzerland's government is providing a guarantee of up to nine billion francs for further potential losses on a clearly defined part of Credit Suisse portfolio.
UBS signalled no quick turnaround for the 167-year-old Credit Suisse, which came to the brink of collapse during the recent global banking sector turmoil after years of scandals and losses.
It said it expected both the Credit Suisse group and its investment bank to report substantial pre-tax losses in the second quarter and the whole of this year.
Credit Suisse faces certain restrictions in its ability to do business until its acquisition by UBS is completed, according to a regulatory filing.
Following the legal closing of the transaction, UBS Group AG plans to manage two separate parent companies - UBS AG and Credit Suisse AG, UBS said last week. It has said the integration process could take three to four years.
